Several things were covered during the green screen demo with Colin McFadden, some of it being technical (which I won't get into because much of it was over my head) and some of it being fairly basic concepts.
1) The backdrop should be fully extended so to minimize the appearance of any wrinkles in the fabric (this makes editing easier).
2) Lighting for the green screen is best when it's evenly distributed and neither too bright nor too dark. Differences in lighting along the screen can make the green appear darker or even yellowish, and can affect clothing, hair, and skin color in similar ways.
3) Don't wear green clothing unless you want to blend in.
Colin seems willing enough to help anyone in need of some green screen time, preferrably during the day or early afternoon. His E-mail is mcfa0086(at)umn(dot)edu, so ask him if you'd like to do anything.