1. Don't think you need to use every single color in the program you're using, be it Adobe Illustrator or the one I use, Paint Shop Pro 7. Learn some basic color theory or if that sounds too complicated, use a few colors and shade with a simple black or a darker shade of the color. Don't be afraid to keep learning and experimenting with new color schemes or mediums like colored pencil, marker, graphite pencil or watercolor.
2. No more pictures of Alice in Wonderland. Seriously. If you plan to make a 'dark, gritty, gothic' version of Alice in Wonderland, do yourself a favor and don't. Not that I don't like "Alice in Wonderland" or "Through the Looking Glass", I do but...EVERYBODY has done it. That ground has been so well-trodden, its down to the bedrock. Personally, I blame this on American McGee's Alice in Wonderland computer game and then being appropriated by Hot Topic in tandem with the Disney version and then getting a reprise with the Tim Burton version but guys...enough is enough. Want to do something unique? Do a dark, goth version of Pippi Longstocking.
3. Sign your work or put a mark somewhere on it, either near the bottom or incorporated into the work. We've entered an age of reblogging and sharing and with that comes not crediting. Some people do it out of laziness, some out of ignorance, some out of a more malicious forethought of taking and then passing it off as their own. Point is, its become a fact of life and unless you're making an anonymous Rage Comic, you won't get credit when somebody decides to put it on their Tumblr and then it gets on Reddit, and then it gets EVERYWHERE ELSE. You may not be able to stop people from taking your work and crediting it as their own or just sharing it around but at least put your signature on it or some kind of mark (for example, my brother signs his 'work' with an Anarchy style 'A'.) If you're super paranoid, incorporate it into the work in such a way that it can't be cropped out without compromising the art itself, i.e. along the character's leg
4a. Be honest with yourself.
4b. Know consciously what your strengths and weaknesses are and actively seek to reinforce the strengths and fix the weaknesses. Come up with 'prompts' to work out of your comfort zone. For example, I've noticed the way I draw legs could be improved so I've been working on drawing classical statues and poses, focusing on legs and the twist of torsos. I really, REALLY, wish my scanner was working so I could show you. :(
(just one of the statues I'm working on)
Those are the only ones I can think of right now. I'll probably come up with more later on.