One of the most important things you can do to prevent injuries is to stretch before starting any physical activity. Here are some easy ones you can do at home before practice and before games.
Ankle Pops: Lightly bounce off your toes, keeping your knees in a very slight bend. It should look like jumping rope, only you'll be moving forward slightly.
High Knees: Take the same stance you'd take when you're about to run, only bring your knees closer to you chest, keeping your entire body facing the direction you're running.
Butt Kicks: Kind of like high knees, only you will be kicking towards your butt and not your chest.
Step Slide: Assume a low athletic position with your feet slightly wider than shoulder-width. Slowly step with your lead leg while keeping the body in a low position. You should stay low and keeping a minimum of six inches in distance between the feet upon returning to the original position. This is similar to a "defensive slide" in basketball.
Back Pedal: Run backwards with a bit of a forward lean.
Knee Hug: While walking forward, hug your left knee into your chest, then step. Then switch to your right leg and do the same.
Source: USA Basketball