I enjoy teaching people about Art, so I'm going to share some of my common tips here. I find I often have to repeat these points to new artists, so if you are new, check these out first. If you want some specific help with a particular drawing, please upload it here and I will check it out and see what I can do for you.
If you're a self-taught artist, there comes a point where it's harder and harder to get better. We want to believe that as long as we keep practicing, we'll keep improving, but the fact is, there are a lot of special techniques that artists need to master because they keep going.
Drawing is Not Writing
Everybody learns to write at a young age, and we write so much in school that it becomes our primary interaction between pencil and paper. When we write, we learn to be quick and precise and we practice making the same marks over and over again until it is automatic.
Throw that idea out the window.
When you draw, that is not how you want to do it. It may be helpful if you're making a daily cartoon, but if you want to make scenes full of different characters and different perspectives, you need to be able to change what you are doing every time, and any sort of automatic reaction can cause you problems.
Think of drawing as more like working with clay or playdough. You start with a basic shape and you have the freedom to add more or take things away or move things around as you get it closer and closer to what you finally want. To be a good artist, you need to force yourself to go beyond the first marks you put down on paper. Give yourself permission to use the eraser and start over to make it better. Spend time with your drawing, really soak it in and decide if it is the way you want it before starting the finishing processes.
I often say "don't think and draw". In order to make the best art, you need to be able to focus on moving your pencil or brush or stylus precisely without having to think about what happens next to your drawing. Plan things out first, do sketches, sketch on top of sketches and do your final version with the utmost confidence that it is exactly the way you want it to be. Do anything you can to make drawing easier for yourself, take measurements, use grids, ink over sketches, etc.
Work from Reference, not from Memory
Ask someone to tell you a story over and over again, and they'll probably tell it a little differently every time. Memory is a really hazy thing, not to be trusted, and Visual Memory is often worse than the rest of it. Your brain is actually designed to throw out most of what it experiences, so this isn't something you could realistically train yourself to do, you've got a million years of evolution in your way.
So when you make art, don't work from memory, work from reference. Look at something and draw what you see.
A lot of new artists really hate this idea. It feels like cheating, or it seems like it would limit you to drawing what you can find. As far as cheating, yeah, that's the idea. Nature has conspired to give you a brain that just can't remember well enough to draw from. The only way to win is to cheat.
As far as limiting, you can delimit yourself by combining references. I like to use the example of drawing a dragon. Dragons don't exist, so how you could draw one from reference? Well, a dragon is basically a combination of various other animals. Modern dragons often have the bodies of lions, scales of snakes, wings of bats, wolfish heads, horns of antelope, talons of hawks, and so on. These are all things you can find pictures of, and you can combine these multiple references into one great dragon. You can also learn to distort references, imagine if that lion body were a little bulkier, imagine if those snake scales were a different color, if those antelope horns were a little more curved, etc. If you have many images of your wolf's head, but none in exactly the right angle, you can probably have enough images to imagine what it looks like in the angle you need for your drawing. And nowadays, you can easily find video of something like a wolf, and watching something like that in motion can help you even more.
In my art classes, I was told to always use references from real life, but I would argue that it's a great help to use the work of other artists while you are working. So you want to draw The Rock in the style of Akira Toriyama, then you need some photos of The Rock and some drawings by Akira Toriyama. As before, combining style references is also helpful, you might want do something like mix Sonic the Hedgehog style faces with Fairy Tail style bodies.
Proportions and Relations
In the same vein, your brain is not fantastic at taking accurate measurements on its own. Even when you're working from reference, it can be hard to draw it in exactly the same way. One of the ways artists get around this is by carefully studying the relations and proportions of various features.
Let's say you were drawing this fox:
In art we often measure things in "heads". Heroic characters stand about 8 heads tall, petite characters about 5 heads tall, chibis 2 to 3 heads tall. This fox is about 3 heads tall, his body is about 1.5 heads across where it touches the ground and his tail is about 1 head across. His legs start about 1 head up from the ground. You can also use relative positions. His eyes start about 1/3 the distance between his forehead and his chin, his snout starts about 3/4 of the way down. You can also look for relationships in the drawing, like front legs are about in line with his eyes, so if you draw a line straight down from his eyes, you'll know where to put his legs. If you know where his front legs are, you can start making measurements based on the position of his legs.
You can also use proportions and relations to build characters from scratch. If this fox's eyes are 1/3 down his face, does it not stand to reason that all foxes have their eyes there? Or if the fox turned his head to the left, his eyes would still be just as far up, right? This can get muddied a bit when dealing with perspective, but ultimately perspective is math and math has rules. You can get a feel for the rules by studying enough references. If you look it up, there are a lot of rules about what proportions to use when drawing human beings. I would take these with a grain of salt, if you make every character by the same stubborn formula, you can end up with a boring gang of clones.
Think in 3D
Think of your subjects not as circles and squares, but as spheres, cubes, tubes and boxes. Do not draw "shape" (2D), but "form"(3D).
When working in 2D, it's natural to only think in 2D. We tend to think of the drawing as a drawing and not as a person or animal or whatever it is and start using techniques that are 2Dimensional. This can work fine for a while, but you will get into problems once you start needing to deal with new camera angles, poses, perspectives and animations. Thinking in 3D is also critical if you want to do realistic shading. Without an understanding of how your subject looks in 3D, you'll end up shading it to look flat and the illusion will be broken.
A good practice for thinking in 3D is to build a character or object entirely out of cubes and boxes. Some people do this with spheres and cylinders, but I would avoid that unless you are going to soft shade them, since a line-work sphere looks exactly like a line-work circle.
When working with humans, try to think about what each piece of the body is really like. What does a thigh really look like? It's more than just a cylinder, right? How? Torsos are worth some extra attention. I often see people making incorrect assumptions and the final result looks very flat, like a ginger-bread man instead of a human being. A lot of artists will go on forever about how learning anatomy is the most important thing, but as long as you are using reference and thinking in 3D, you will pick up what you need to know without making any special effort to learn human anatomy.
Art is Narrative
As you get into more advanced topics like artistic composition and selecting poses and whatnot, the most important thing to remember is that the purpose of art or imagery is to convey information. A picture is worth 1000 words. A picture says something. Before you start working, make an effort to decide what it is you want your image to say, and then do your poses and composition and so forth to match that narrative.
Make sure that your artwork is saying something interesting. If you were reading a story, you wouldn't want to read a chapter about the texture of a brick wall. So when you're drawing, it's okay to make a really nice brick wall texture, but don't make it "louder" than the action or main subject of the scene. Exaggerate the important, abridge the unimportant.
A good story, and a good piece of art, is not about portraying things but about portraying emotion. Don't just draw people, draw people who are feeling something. If you portray an inanimate object like a car, don't just portray the car, portray how the car makes you feel, excited, disappointed, nostalgic, etc. There are a lot of ways to do this, best way to start is to study, see how an art makes you feel and compare it to artwork that makes you feel differently.
Check this out:
This is from a genre known as "pulp", cheap thrills on cheap paper. It was notoriously over the top in order to attract customers to buy whatever was behind the cover, not unlike modern click-bait. But pulp artists learned to capture emotion incredibly well, and it's a great reference to study.
There's a lot of emotions going on in the scene. The most obvious is the girl. Wide-eyed and intently focused, mouth agape in a scream, head thrown back, fingers spread and legs balanced as though ready to fight or flight, it's clear that she is not only afraid, but any thoughts besides fear are absent from her in the moment. The knight in the lower left is looking worried, it seems that he fears for woman's safety and we can predict from there that he is here to save or protect her. The other warrior grimaces and looks intently at the knight, suggesting that he is struggling in his fight, perhaps becoming unsure of his ability to win. The abundance of diagonals and unbalanced weight tell us that the knight and the warrior are in the midst of action, and swords and axes tell us it is a conflict worth killing or dying for. And most interestingly in this scene is the emotions we get from the disembodied arm holding the torch. Even though we can't see the face, the tense muscles and arm held ready gives its alleged owner a sense of determination. And perhaps the various reactions to him throughout the scene strengthen this deduction. The relative placement of each character is also important. The torch-holder is at the top of the scene, giving him a sense of power, while the knight is the lowest, making him seem relatively weakened.
Combine the high emotions with the dungeon setting, and we have a very clear idea of the narrative behind this image. Critically, it is difficult to guess what is going to happen next. After all, that was the point, to lure you into buying the book to find out. If you wanted to, you could use what animators call "anticipation" to suggest that something is about to happen. Perhaps instead of fixating on the torch, the girl could be looking at a weapon on the ground, suggesting she's about to make a move to save herself. Or instead of looking at the girl worried, the knight could look at the torch-holder with a look of determination, suggesting that he is about to take some action against him.
Now, you don't always want to aim for the outrageousness of pulp, but it is important to be obvious. Going back to the concept of narrative, we often say that a good image "reads well", meaning that it's easy to tell what the image is supposed to say. One of the ways you can do this is with strong silhouette, meaning that if you simply shaded a character completely black, you should still have a decent idea of what they are doing. Avoid layering important elements on top of each other or crowding out important elements with unimportant ones.
Avoid Exactness
Especially when dealing with living things, you rarely see anything that is perfectly straight, so don't try to draw things that way. Avoid standing up completely straight. Don't look directly at the camera. Don't place arms or legs perfectly symmetrical to their opposite ("twinning"). Make shapes with curves, tapers, s-shapes instead of perfectly cubed or rounded or whatever.
Differentiate
Especially when you start drawing something like a comic or video game that has multiple characters, or characters in various states, it's important to differentiate so that you can tell the difference.
An annoying number of artists don't differentiate much when it comes to character design, an affliction I call Sailor Moon Syndrome. If you told me that the sailor scouts were all the same character who just changes hairstyle and wears different colors of the same outfit, I could believe you. Different characters should look different! Facial features, body proportions, etc.
You also need to differentiate when showing different states of the same character. Most obvious example is showing emotion. There are 43 muscles in your face, and you use them all. Going back to the idea of narrative, you need to make your different emotions easy to read and easy to distinguish from each other. Emotions aren't limited to the face either, hands and shoulders also speak volumes and the overall pose or "line of action" also indicates how a character is feeling. Another example of a state might be a character in the midst of action. Walking vs running, slapping vs punching, etc. Each state should bring several changes to the character, and the character should have a variety of states. Running with your pet dog on the beach should not be the same as running away from a scary tentacle monster.
A more advanced way to change emotions is with timing. Imagine someone bursting into rage in a split second vs someone slowly going from calm to annoyed to angry to explosive madness over the course of a minute. Or a character is looking at a selection of vegetables at a grocery store. She looks at potatoes and onions and cabbages for only a split second, but then gets to a cucumber and her gaze is locked on it for a really long time. I know this isn't easy if you're not doing a full on cartoon, but there are ways. Comics and video game dialog have ways of simulating time.
If you get into more animation and acting, human beings actually need to move their faces to think. Go to the mirror sometime and try to think about different things, like doing math in your head compared to thinking of rhymes, or reciting a story from memory compared to making one up. Or better, ask someone to think about these things without telling them why.
You can also use emotions and states to differentiate characters. Everyone gets angry or happy sometimes, right? But not in the same way. Image Sonic the Hedgehog and Shadow the Hedgehog. In a neutral mood, Sonic wears his snarky smirk while Shadow has a perpetual scowl. In a happy mood, Shadow will give you only a hint of smile, while Sonic would have an ear-to-ear grin. Get them sad and Sonic's not afraid to show his manly tears, but Shadow would probably just gaze off into the distance and mope. Even though the characters are feeling the same emotions, they show them differently. For those of you that do your own writing too, different characters change emotions differently. Shadow might get cranky at any little disturbance, but never get really angry, while Sonic might not get bothered by little things but absolutely lose his mind when something major angers him. Likewise with states. A really plain example is the differences in how Sonic, Tails and Amy Rose move around. Sonic leg-wheels, Tails serenely glides through the air and Amy has an all-too-exaggerated girlish gait. And even though Shadow is a clone, the designers gave him a different run cycle to differentiate him.
Another point of differentiation is how characters automatically act around other characters. Take Leela from Futurama for example. Around Bender and Fry, she tends to have her guard up, expecting some sort of buffoonery at any moment. Around her pet Nibbler, she is completely infatuated by his cuteness, and acts like a frolicky schoolgirl without a care in the world. Around Prof. Farnsworth, she is respectful and pays attention, because she wants to be good at her job. Each other character in the show has completely different automatic responses to other characters. Some characters, like Prof. Farnsworth and Zap Brannigan, have more or less the same reaction to almost any other character, which actually gives them the sense that they have their head in the clouds and aren't really paying attention to the people around them.
