* You are not an artist unless you draw regularly. 'Artist' is not some title. It is a term describing something that you DO. A musician is NOT a musician unless he plays. A writer is NOT a writer unless he writes. If you do not draw/paint/whatever, you are NOT an artist.
* You will NEVER EVER EVER get better unless you practice, and practice a LOT. Every single day. Being an artist is not a thing that can be so easily picked up. Just like with anything worth learning, you have to do it. Over and over and over and over again.
* Most of what you draw, even with practicing, will be utter crap. Maybe one every 30, 70, 100 sketches you do will turn out well. Maybe you'll be lucky and get it sooner. But generally, practicing helps you be more accurate to get those numbers down, and will make you get the crappy stuff out of the way faster, so you'll start producing good stuff every day.
* If you do not LOVE to draw, DO NOT DO IT. Art is a very thankless career/hobby/whatever. Unless you have a passion for it and need to draw for yourself, without any sort of praise or monetary anything from anyone, do not expect to go very far. YOU must enjoy it for YOU, or it is completely pointless.
* Art blocks are frustrating. Not having inspiration is frustrating. Those 70-or-so crap sketches you have to get out of you are frustrating. But you have to keep drawing or you won't get through it. That's the ONLY way to get over it. Take a break, yes; try something completely different, yes; but unless you keep it up, you lose your being an artist. You can't expect to get anywhere when you can only draw when you are 'in the mood'.
* I don't think I've met anyone who's ever truly satisfied with their work. They may come out with a piece that they really like and enjoy, but really? Never happy with it. This goes for the greats that people admire and everything. Everyone is trying to get to a higher level, and just because they're better than you doesn't mean that they have it easy. Quite the contrary, really; they're stuck learning the REALLY advanced stuff, trying to make it work. Being jealous of someone else's personal 'failures' is STUPID. Art isn't a race; it's getting better and comparing you to yourself, not to anyone else. Thinking otherwise is very petty. Learn from them, be inspired by them, but do not hate them, or put them down when they are honestly unhappy with their quality of work. We're all trying to improve.
* Figure Drawing will help you immensely. Possibly more than anything other than practice, figure drawing improves your skills on so many different levels. Take it in school, see if a local art museum offers classes, make yourself draw other people, hire a model, do SOMETHING to get figure drawing in your routine, and often.
* Real media will help you on the computer, and the computer will help you with real media. Do not limit yourself to one or the other; being proficient in both ensures that you can do a variety of things to achieve the best possible results.
* Art is not art unless you get messy sometimes. Try painting and make a mess. Even digitally, go out of the lines and clean up later. One of my very favorite things is drawing with pens.
* Draw with pens OFTEN. Don't let yourself get caught up in trying to be a perfectionist; this hinders you in sketches! Sketch messy, FEEL what you're drawing; you can refine or redraw later. Sketching should be fun and liberating, not crushing under the oppressiveness of needing to get it perfect and without any blemish. A sketch is a sketch, and has so much more life when you let yourself mess up.
* Art is 30% drawing and 70% observation. Look around you. Draw from life. Photos are great and all, but nothing beats real reference. Go to a park and draw the people and trees. Go to a zoo and draw the animals. Spend time drawing your pet. This will help when you want to draw from memory, and like figure drawing, helps to hone your skills.
* Art classes are not stupid. You may not come out of there with works you want to show off, but they will help you experience a broad range of techniques and styles, and give you access to materials and opportunities you might not otherwise have. If nothing else, treat art classes- even the really boring ones - as a chance to get more practice in... and this can only be a good thing.
* Flashy coloring is NO replacement for good, solid principals in art. Learn the framework of how art is made to form a solid foundation, then take it and run with it in whatever way your creativity desires.
* Make sure to draw for yourself once in a while, even when doing commissions and the like. Please, please, please enjoy your art. Let it remain yours, even when in the service of others and careers.
* Don't be afraid to try something new. People might give you flack, but art should be something sacred to you. Stand up for it. Take it where YOU want it to go.