The number one and most important thing to remember when drawing is: Art isn't made in a vacuum. Expecting to magically just know how to draw ponies without ever having copied a reference is like expecting to magically know math without instruction or books. You'd have to create every single math theorum that everyone has ever made or you'd like to know from scratch. It takes critiques, feedback, referencing, and more. Most of all- it takes practice. Practice practice practice. Make bad art. Make mistakes. Its the only way to learn. You can't and shouldn't ever expect yourself or your art to be perfect.
Taking criticism is hard. I used to equate critiques as akin to putting one's face in a blender. Now, I starve for them. It sucks to have something you poured your heart and soul into ripped apart in front of you. What you have to realize is that: A. we are only trying to help you learn more so you can get better and B. we aren't attacking you personally Ever.
There are many common problems, here's what they are, why they occur and what you can do to train yourself away from them.
Common thoughts
The Horizontal problem
All the other problems here come from this problem. We all have a habit of wanting things to be straight, up and down... orderly. This is an especially true desire for the brain when creating. This is silly. Unfortunately to add insult to injury our eyes are trained to follow straight and horizontal and vertical lines. We follow them right off the page. Horizontal and vertical lines aren't necessarily bad, but just be aware of when you are using them. To contrast, diagonal and curved lines are more dynamic and add movement and interest to a piece. They aren't a goal necessarily, because too much can be a distraction.
Stiff, blocky looking figures
This is almost like the horizontal problem. Making figures straight up and down (The legs go down, head faces forward, eyes looking straight ahead) makes the figure look boring. There's no interest. Try and make the head at a different angle from the body which is at a different angle from the legs. Vary things up. Variety is the spice of life.
Symmetry
This is hard here because you're working from a cartoon and they're pretty symmetrical looking. The same problem is here as the blocky figures. Its just boring to look at. Yep, there's a leg. Yep, there's the same leg on the other side.... Yep... Try to vary things up, put one leg at an angle, push an eye off into perspective, tilt things at an angle relative to other things or make an ear flop, make one smaller or more hidden.
Keep in mind, the mind follows lines.
If the line for the hair coming down continues on through the face, the viewer has trouble separating them and they start to look like the same object. Try to offset lines from one to the other. Or not. Just be aware of what this does.
Never be afraid to ask for advice.
If you get frustrated. If something looks off and you can't tell why. For any reason. This is the easiest way to never make the same mistake again.
If you know it looks off anatomically, the audience knows it looks off.
This is, unfortunately, always true. For help with this see identifying compositional awkwardness.
On anatomy
Use References
This is The Best Way to Learn. Copy from a screenshot (don't call the work yours of course). You can't expect yourself to know how it looks without having drawn how it looks.
Pony leg directions.
They are rarely if ever straight, and never straight up and down this misconception comes from 1.a.
Pony ears
They attach towards the back of the head, so when looking at the front from underneath or in a 3/4 view the head is more forward.
Thinking like an artist
Art is not Precious
This is especially true when making art. You're obviously already capable of drawing that thing you just drew, so you can erase it to fix its position/perspective/angle/proportion/everything about it. and you'll be able to draw it faster and better and have learned something from the experience. Drawing today isn't about making an awesome final product today, its about learning how to make an awesome final product tomorrow. Tomorrow never comes but if you happen to accidentally make a great one today, great!
Art is fear
There is an excellent book shown here called Art & Fear. For those who are frustrated with art or find themselves bogged down or intimidated by art, or just want to understand what the process is, I recommend this book. Its short and unnervingly accurate about the way you think when making stuff.
Keep the world in mind
Forcing yourself to make art in a vacuum, devoid of all contact, inspiration, references and creative exercises is really really bad.
I can not be redundant enough about this.
Set long term goals
This is for those serious about learning, but is still good to keep in mind for everyone. It is inevitable to be frustrated or put off doing art. In order to avoid this set an attainable goal in the far future. 'Get better at coloring by June' or 'be able to draw the mane 6 from memory by October'. Set a bunch of mini steps in between now and the far off. Work for an hour a day. Just an hour. You'll be surprised at how quickly time jumps ahead when you're not looking.
Exercises you can do
Measusing and Comparing
How to measure and compare (by dispatchrabbi). To get angles, proportions and scale right from a reference use a pencil to compare angles between a reference picture and your piece. Hold the pencil up to the reference to get the angle, then back to your work. If you do this while working, you'll notice that it becomes a lot easier to correct mistakes that 'just don't look quite right.' This takes a lot of the guesswork out and makes proportions and angles much easier.
Do this everywhere. The angle from the ear tip to the rump. From eye to muzzle. From front to back leg. Between any two arbitrary points or to get the angle and/or placement of a limb or eye or tail. Absolutely positively everywhere. And then erase. Mark, erase, correct and repeat. Don't get bogged down by working too long in one area. Get an almost right foundation and move on. Corrections and refinement come with the process.
There has been some confusion on this, so let me expand. When I say angle I don't mean relative to horizontal. Draw your line. Hold the pencil up parallel to that same line, invisible or not, that you are measuring on your reference. Bring the pencil over to your piece without changing its angle. Compare what the pencil is to what you have. Correct with said pencil. Repeat.
Gesture Sketching
How to gesture, a process guide. This is another reddit guide that goes into the details of getting proportion and scale correct while giving advice on drawing quickly. Fast fast fast.
Shading
Shading, everything shading. Actually just the beginning of shading. But its a nice exercise to follow and learn from.
This guide here goes a little more in depth on what shadows really are and how to work them into art.
Where to shade goes over breaking down the pony into simpler shapes and what shadows within shadows really are.
Critiquing
How to critique and how to take critique. Artists and critiquers should take a look at this. It doesn't only have etiquitte, but actual advice on how to help others improve.
Common problems in critique? This guide here goes over that.
Pony Anatomy
The basics. A guide on pony anatomy and undersketching. Exactly what it says. It is a good place for those who really want to capture what an MLP pony looks like.
Composition
Composition. This guide is a compacted version of 2d design. Really good for inspiration.
Feel free to post questions, pieces for critique, and anything that crosses your mind in this post.
This guide is meant to be advice only. These are things to be aware of, not to follow like strict rules of adherence. Ignore all the words you like, but if you come to me, this is the advice I give.
Last things last, fellow critics help me to write this guide! It is not (and should never be) done. If you have links or ideas submit them here or PM me and I shall append the guide.