If your in Nebraska now (by your profile) you should have football coaches and trainers coming out from behind every tree in the state to teach football basics. That's from even when the kid is still in the womb. Nebraska is a football state...big time. Interesting question any way.
Football exercises/drills include leverage, balance, foot and lower and upper body shift positions (not unlike judo moves surprisingly) and push and pull drills. If positioned correctly, even when moving, it will be hard to be knocked around. One on one or two on should be taught hands on. Paying attention to what is going on around you, and getting ready for it, at the time of a play is of major importance. All these can apply to any position you play.
If trying to improve with lifting exercises on your own than consider walking lungs, step-ups, one legged squats, clean & jerk, snatches, etc. Standing/squat jumps, bench/table jumps, rope skipping standing on a narrow space (bench, box, etc), rope and tire drills, low beam walking, etc.. The more you practice the better you get. Good Luck.
