In order to change the song in the background, hold X and hit the left or right trigger. This only works while you're not in a game.
In order to get a team's cheerleading card, you must complete that level in mini-camp mode. Note: Not all teams have pictures for their cheerleaders, but they all do the same. (Pump up the croud for your team)
This way is very easy and it will never really backfire on you. You have your defensive line. Take a guy from one side. I usually take the Right End and move him over outside of the Left End. It works either way if you wanna move the Left End. Anyway now if there is no Tight End you can just get right in there and disrupt or sack the QB. Even if there is a Tight End on that side he is way easier to plow over than the lineman that you line up against at the start. The only way this will backfire is if they run the ball to the side that you just left open. Then there is one less guy to make a tackle and the CPU can get more yards or even a touchdown but if you have good DB's and LB's you should be fine.
Go through Football 101 to rack up on easy tokens. Once you get a play down packed, you can run it a couple more times to get even more tokens. These can go towards Madden cards, which can be useful on the field!
Whenever signing a player, make sure you give him a 7-year contract and put his signing bonus all the way up. As long as your team is winning, you can pay for his contract and thus, keep a lot of room under the salary cap.
Once a player retires, there's a good chance that he'll come back as a coach somewhere down the road. Not all retired players become coaches though, but most of the star ones do.