While in the Slam Dunk Contest, tap X, then hold B to do MJ's 1988 Slam Dunk. If 
it is done from the free throw line, it is worth an automatic 50. Hold LT + RT 
and press X(2), Y to do the Vince Carter arm in the rim. If you hold it for a 
few seconds, he will put his arm pit in the rim for a 50 sometimes.

To do a 720 dunk for an automatic 50, hold RT and run towards the basket and 
press the one foot 180 gather (Y). As soon as the gather motion starts, quickly 
rotate the Left Analog-stick counter-clockwise, twice then press the Windmill 
Dunk (Y) again. Release Y just before completing the first rotation and you will 
automatically complete the second rotation. You will always get a 50 for 
completing this dunk. Note: The RT dunk modifier must be held for the entire 
dunk. Also, you must complete the 720 motion before pressing Y the second time 
to dunk.

To do a under the legs dunk, start from the baseline. Hold LT, then use B to 
gather and B to do the trick. Correct timing is required.

To do a under the legs reverse dunk for an automatic 50, start from the corner 
of either baseline, then run toward the basket and press the two foot 180 gather 
(A) just as you reach the word HOUSTON*06 along the baseline. As soon as you 
start the gather motion, hold Pump Slam (B) button, releasing B as soon as the 
ball passes under the legs and make contact with the player's other hand. The 
timing is difficult and you will probably get hung on the rim until you get the 
timing correct. However, this dunk is worth an automatic 50. Note: When you 
perform this dunk, make sure you are running in the red out of bounds area 
behind the goal and not on the court or the judges may only give you a 49.