[buickbeast]

The best defense is a time consuming offense. Even if you run no huddle the entire game, run the playclock down under 7 seconds and stick to your gameplan even when your down 14 points, especially in the first half. Don't play the score, play your drive.
When you are on D, set your team to conservative for big hits and don't go for fumbles. Manipulate the ball carrier to run towards your defenders for a gang tackle, do your best to wait and not have to try a solo tackle.
If your playing against another person, control the game by making them play to their weakness. For example, if they like to run a west coast type offensive, play short zones and force them to pass it deep. Run a lot? Dare them to pass. Also, you don't need to get sacks, just make the QB uncomfortable.
I know it's easier said then done. If nothing else, minimize your mistakes. You don't need to beat the other team and yourself.