Easy Win Bug
If you get ahead in the score, a glitch can get you an easy win. Simply swim behind your own goalie and wait, as everyone else returns to the other side and swims in circles for the rest of the game. If an opposing team member follows you, either outrun him or use a break technique and he will also leave you alone.
Recruiting Opposing Team Members
If you see an opposing team member that you want on your own team, scout that player to see how many games remain on his contract. If you repeatedly challenge the team -- playing and forfeiting repeatedly can bring this about quickly -- make sure you save your game before his last game. Scout that player during his final game, and afterward, he may get re-signed or released. You can find the player and recruit him if he gets released or otherwise reset the game if the team re-signed him and try again.
Easy Experience
Passing the ball between players gains some easy experience points. Tricks such as those in the easy win bug, putting the main three defenders asleep with "nap pass" or going to one of the corners in the right end of the field, keeps the opposing team from interfering with your team. Pass the ball between the players you want to level up repeatedly to gain easy experience.
Easier TechCopy
Players learn techniques by copying them from opponents. As the TechCopy option flashes above an opponent, press the circle button just before pressing the X button to make the TechCopy more likely to succeed.