When in the main menu screen, type "REDROVER" in all lower-case. At this time you should hear a noise.

MICHAEL JORDAN, THE EASY WAY
Pick a player in superstar mode against Jordan. Set the game match to 11pts. At the controller setup screen, select Jordan as your player. Let the other player score 10 points against you, then switch the control back from Jordan to the other player. Now all you have to do is score 1 point on Jordan.

MICHAEL JORDAN
Defeat Michael Jordan one on one in superstar mode to unlock him
on the roster.

ISAIAH THOMAS
Get fifteen steals in a game in superstar mode to unlock him on the roster.

Easy Scoring: 
Pump fake to get your opponent to jump. Now just go for a dunk or any other pretty looking move.

Practice Courts:
At any screen before game play begins, type "Playground" to play at the night court or the daytime practice court.

To unlock Larry Bird you need to get at least 20 points in the 3-Point Shoot Out in Superstar. Try using Glenn Rice from the Lakers, or John Stockton from the Jazz. Use as many chances as you can get - set it up for 8.