I spotted these green screen tips from Brian Richardson (he of WhatTheCast and Dragon*Con TV) in the famous Yahoo Videoblogging Group. I think they will be helpful for anyone doing puppet podcasts who is a little mystified/frustrated by the green screen process:

• The main trick is even lighting across the screen and the people in front of it. Much like a Babylon 5 episode, shadows are the enemy.

• Try using four lights on your screen. Two 1,000 watt softboxes are good to light your green screen and two 500 watt umbrella lights can be used to light your subject (if you’re not familiar with the difference between these types of lights, try Googling them).
• A learn what colour temperature is. All of the light bulbs in your setup should use the same color temperature (I use 3200K).
• Don’t get too close to the green screen. Once you get within three feet of the screen, shadows start to form and they will mess up your key.
• Another trick is to take your camera off of automatic. Letting the camera adjust color/white balance in the middle of a green screen shot might cause problems editing (the value of “green” will change as people move in & out of the scene if the camera tries to adjust).

Want to try creating some green screen effects, but don’t have the right software? Check out this green screen tutorial on Instructables that explains how to create green screen effects using Debug Mode’s WAX (it’s free to download).