I improved my agility during pick-up football, basketball and baseball games growing up. When you play pick-up games (or street ball), you don't think about technique---you just play the game. Consequently, you improve your agility skills (if you do them correctly).
You can work on your agility and speed during any pick-up game. You don't have to wait until your formal team practice to get better. Matter of fact, I learned much about how to compete by playing pick-up games with older guys. You either got better or embarrassed!
Improve your agility with these drills and then apply them during your movements in a pick-up game:
1. jump rope (one foot, two feet, slalom, Ali shuffle, backpedal)