Get Seoul Stadium
Win the International Cup.

Win a stadium
All you have to do is win the championship club with a club and you will get a new stadium.

Unlock Stade de France
Win the club championship, and you'll receive the Stade de France stadium.

A massive head start in a football match
When you are playing a football match press start on your controller, then go to select sides. With the left thumstick choose the team you are against and resume the game. Then score lots own goals(as many as you like), then select the team you were in the begining and play on. (This tip should work on all systems)