Put the 2X on, get a monopod if you can, if not, shoot handheld.
Set center-point only AF, AI Servo, Av, your goal is to shoot 1/1000 or faster.
Shoot the team coming on to the field.
Initially, try setting up about 20-30 yds downfield in the direction your team is moving the ball, shoot away, trying to get faces of kids with the ball or tackling. When they're on defense, you're the opposite, behind the opposing players, now trying to shoot a tackle. You'll get a feel for it........... e.g. when the ball is inside the 20, shoot them from right behind the goalpost, if you can.
If you need to shoot every team member, pay close attention, shoot every player going on/off the field.
Shoot your cheerleaders as well; they buy/want photos.
Enjoy.
EDIT: To what dekalb sez below -- set the monopod so that you're on one knee, the lower your angle with kids, the better the shot.