I'll be honest, greenscreening ain't easy. I have a greenscreen studio setup in my basement; it works... but not great. The best advice I can provide is light evenly! Get some powerful work lights from the Home Depot or Lowes and and set them up at all different angles to make sure the screen is evenly lit.
Also make sure you have a sufficient DV camera. A cheap 1-chip camera will not work well. At the very least, I'd recommend a Canon GL2. However, even that is vulnerable to the 4:1:1 problem. You can read more about the problem and potential solutions here:
http://www.neopics.com/bluescreen/
As for software... depends. I use Apple Shake, but it only runs on Linux and Mac OS X. For PC, check out After Effects. It has some pretty effective compositing tools. If you want a dirt cheap compositing program, check out Chromonator at fxhome.com . It's tailored for low budget compositing.
Here are a few other useful resources I've stumbled across over the years:
http://www.philipwilliams.com/greenscreen.aspx
http://www.channel101.com/tutorials/...tutorial_id=19
http://www.jushhome.com/Bluescreen/Bluescreen.html
Best of luck with your greenscreening. If you need any help, feel free to send me an email at
av11d@mac.com; I have a lot of experience with cheap compositing techniques.