Weight lifitng exercises? For Football player at 13?

I play football and I want to get bigger and stronger. I currently play Center and Defensive End. Im 13 and weigh 155 pounds and im 5'9". I know that you mainly use your calf and thigh muscles in these positions but what are the best ways to improve these areas. I already do squats and lunges but are there any other exercises? And if so how much weight should I be using to do them?