If you are struggling to win games, I have found a little trick that will almost guarantee you a goal every time:
When their keeper picks up or catches the ball, run and stand in front of him with your striker (or whoever is closest at the time). Then when he goes to kick it, run forward and you want to be running past him (kinda through him) just as his foot connects with the ball. If done correctly, you'll be running into the goal with the ball at your feet. 1-0.
Also, if you're about to lose the game, hit the Start button, wait a few seconds, hit the Back button, and the game will reload and you can play the match again.
EDIT: thanks to SKIN RIP for this: "Just in case anyone was wondering u need to win in normal time, extra time and penalties do not count as a win"
This can be won either by playing quick matches, or by going through the Leagues or Cups on Top Player difficulty. As long as they are won within the 90 minutes.