Select the 'Features' option at the 'Main' menu followed by 'Locker Codes'. Then enter one of the following case-sensitive codes (without the quotes) to enable the corresponding effect. Note: Some codes may eventually expire.
3,000 VC : Enter 'N14PS-EXCA9-J1VC1-LEGHF-8U29H'
Sprite Lift Off Dunk Package: Enter 'SPRITEBUBBLES'
Sprite Hang Time Dunk Package: Enter 'SLPERBIRTOEN'
Harrison Barnes Dunk Package: Enter 'HARRISONSLAM'
Random MyStore Item: Enter 'N14PS-ZTQHR-DXPAC-H4Y5H-6NWGQ'
Random Shoes: Enter 'N14PS-AFMAR-LTUHV-4NI38-ASN7Y'
Random Clothing: Enter 'N14PS-XATTQ-LER7J-TJY8Q-NGVFU'
EDIT: April 2014 - Looks like these codes may have expired now, we'll look out for some new ones and post them here.
This is an easy shot to do and is effective against a variety of different players. To perform it you need to rotate the analogue stick in a quarter circle from your ball-hand to the hoop and then back to your ball-hand.
When you need to get rid of defenders the following trick which changes your shots in mid-air works well. To perform it you execute a normal Dunk or Layup and when your player reaches the mid-air point you hold the right analogue stick in any direction.