Always know that you have room for improvement. You can't always be perfect. Work hard to achieve your dream - you don't get anywhere by slacking off. The only physical attribute you cannot change is your height. Your size, musculature, speed, strength, explosiveness can all be improved by a year-round commitment to strength and conditioning, never allow anyone to talk you out of a position or playing football as a result of your current physical stature, you can make yourself into what you need to be (NO STEROIDS, no sport is worth an early death!) Play football with your knees bent, you need to keep your joints bent to use your bodies muscular power, straight knees and hips risks injury and is ineffective, focus your training on developing powerful, explosive legs. Get to the point where you can squat double your body weight for 10 reps; if you can do that, you have very powerful legs for your size, and your ability to execute in football will be vastly improved Also if defensive lineman, linebacker, corner-back, or safety, pretend that it is your last hit or last block and you want to leave knowing you put all your strength in that hit or block like it was your last. Always have a fantastic attitude. A bad attitude is depressing to the team. Be a good sport. Never give up, even if you don't do well at first. Playing football with friends at a park is good practice. You're not pressured to do your best (though you should anyways), it's fun, and you're still getting exercise and practice. Execute everything at practice like a scout from your dream college is looking right at you, be so aggressive that your coaches yell at you to calm down.

You should rephrase your question as to what kind of football tips you want. Eg. running with the ball or being a defensive lineman looking to get to the QB etc.