These are a few bits of advice I would personally give to new artists here. Please take no offense, this is based on my personal experience.
First, I would like to echo Jewelwing and and say patience, patience, patience. When I first came to Woot as a 'hitchhiker', I had very unrealistic expectations of how long it would take to print. (many of you recall this) It is very easy to get discouraged in such a big pool of competitors, some of whom have major chops and/or big fanbases. Since I have been here, I've seen some hard-working, determined artists break up through the ranks and nab a print. Dont get down on yourself or stop competing. The derby with your name on it will show up!
Secondly, try new things with your art. I often see statements of "I draw what I like, the way I like it", followed by "Why dont people like the way I draw?". This is a tough one. We all have our own tendencies and styles, our own influences. This doesn't mean you have to draw things or styles you dislike, but try to find a middle ground. The Woot audience is your customer, make them want what you've got. Don't stonewall them, or yourself. It's important to try new things to see what they respond to, and to see if it's something you like doing too.
Lastly, try to stay focused on the art. Steer away from negative conflicts or politics on the forums. Above all, people are here to see your skills. Interaction can be a great thing here, but keep it positive and respectful, no matter what. Avoid sticky topics that do not concern you. (goes back in time to drill this into my own head...9_9)
For the Woot staff, an improvement I would personally like to see is 'sticky-ing' posts in the forums. This would help artists find info about halftoning, art programs, or where the nice shirt comp file is, etc. Something else that might be nice is, once a month, ask a Woot artist do a short demonstration or tutorial about a technique they use. Even having an artist talk about their influences can be great to read about. It creates interaction and gives artists some visibility outside of the derby.