It is important when setting up your green screen that you get the fabric as wrinkle free as possible. The most effective technique is to use a steamer. Make sure it is hung evenly and that there are no unnecessary folds. Wrinkles and folds can cause disruptions in the image once it is placed over the green screen in post production. Also make sure no part of the subject is green including clothing and props. If there's a similar color it might display the background image instead of the subject. This is why there is a blue side. Also when you place the subject in front of the green screen, make sure there is enough separation so you can light the subject and the green screen separately.
It is critical to light the green screen and the subject separately. Light the green screen first. Any shadows on the green screen will not key correctly and will cause holes in your image. No part of the green screen should look brighter than any other part. This means you need multiple lights. The simplest lighting technique is to place one light on each side of the screen. Next light your subject, taking careful precautions to ensure the lighting of your subject does not interfere with the lighting of the green screen.
Besides proper lighting and set up of a green screen, there are also some important considerations in order to have a solid product after post production. Consider the perspective of the subject compared with the image that will be displayed in the background. Otherwise the subject might look to big or too small to match their background. Also if the subject is lit brightly, but the background is at night time, it won't look good. Match the lighting of the subject in the studio to the lighting of the background it'll be in front of. Depending on the editing program you use there will be options that allow you to tweak the effect. Experimenting with a sharper contrast is usually one of these options and can make a big difference on screen.