It's important to get the production portion of your green screen shoot correct as getting this wrong can make a successful edit all the more difficult.
Mistakes to avoid:
1. Hot spots on your green screen, try to maintain an even soft light spread evenly throughout your screen. Solutions for soft lighting include the use of diffusion, kino-flo, creating distance between the light source and green screen, or bouncing the light.
2. Having shadows on your green screen. Avoid this by separating the subject as much as possible from the screen the creating depth. Ideally, you have two lights with diffusion illuminating the subject from opposing sides, and two overhead lights pointed towards the green screen (note these light will also have diffusion, as to avoid hot spots). The overhead lights will lift any potential shadows cast by the subjects lights.
3. Getting green hue bounced back onto your subject If you stand the subject to close to the green screen some spilling of the green can occur and reflect on the subject and make it an issue to key the chroma correctly in post-production.
Tips for a successful green screen shoot:
1. Have depth between the subject and the green screen. Having the screen slightly out of focus is beneficial in removing imperfections such as wrinkles or marks.
2. If possible shoot with a flat profile. By shooting flat, you lift your shadows and lower your highlights giving you more room for error with regards to your lighting.
3. Keep your green screen wrinkle free. Wrinkles create creases and shadows that make the post green screen removal tedious.