Create a player, then you can trade him or them for player(s) you want.
Example:
QB #18 Peyton Manning 94
for QB #13 Dan Marino 94
Usually they'll say yes, but i never got Peyton Manning.
Low salary cap
Players might want $10.00(TEN MILLION) a year but create a player and he will want about 6-9 million.
Unlock Extra Stadiums
On the matchup screen of a Preseason game, press SQUARE to go to Preseason Options. Press L1 to Toggle the Home Team as the default stadium. Then scroll to the stadiums you want to unlock. Enter the following codes to unlock them:
Stadium - Password
Old Carolina - CAROL
Good Ol' Days - SEPLA TONE
Galactic - GOVT OWNED
Old Denver - 5280 FEET
2050 - LIGHT YEAR
Old Detroit - AUTOMOBILES
Unknown - EMERALD
Old Chicago - WINDY CITY
Old Los Angeles - ANGELS
Old Miami - ORANGES
Old New England - SALEM
Graveyard - RISING
Space - LUNAR
Pop Warner mode - MUNCHKINS
Win a game
Lower the penalties and everytime you make a touchdown, you can do little baby onsides.