Have fun, and don't be afraid to try things you're uncertain about. It's like puzzles, sometimes. Always try and exhaust all of your possible solutions-- if you have an idea for something that you think might work, do it, because oftentimes it'll turn out awesome. ;3
My tip would be this: Take no shortcuts. The reason good art takes a lot of time is because people put a lot of effort into what they do. Whenever you do something, ask yourself, "what would a good artist do?" And after you answer, ask yourself, "okay, now what would a great artist do?"