While in the Slam Dunk Contest, tap Square, then hold Circle to do MJ's 1988 Slam Dunk. If it is done from the free throw line, it is worth an automatic 50. Hold L1 + R1 and press Square(2), Triangle 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 R1 and run towards the basket and press the one foot 180 gather (Triangle). As soon as the gather motion starts, quickly rotate the Left Analog-stick counter-clockwise, twice then press the Windmill Dunk (Triangle) again. Release Triangle 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 R1 dunk modifier must be held for the entire dunk. Also, you must complete the 720 motion before pressing Triangle the second time to dunk.
To do a under the legs dunk, start from the baseline. Hold L1, then use Circle to gather and Circle 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 (X) just as you reach the word "HOUSTON*06" along the baseline. As soon as you start the gather motion, hold Pump Slam (Circle) button, releasing Circle 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.