Actually, you should find lots of discussions on chroma keying in the Vegas forum by searching on chroma or green as a keyword. I don't know movie studio, so I'm not sure if any of the techniques for Vegas will apply though. Basically if this was Vegas you'd shoot your footage, apply a chroma blur, some secondary color correction and the chroma keyer from the video FX. If you've lit things correctly, and positioned your subject sufficiently far from the green screen, this will usually produce a fairly tight key.

You may also want to check out www.fxhome.com - I've been using their Chromanator product and I'm very happy with the results, especially given the cost of the product. Chromanator gave me much better results than Vegas - and I can't think of any reason why it wouldn't work fine with Movie Studio. They have a demo version you can download.

Oh, also think "green" - video cameras respond better to green than to blue, which is why you typically see green screen in video.

--Scott