When you get the ball, go behind the three-point arch and wait until your man gets on you. Then, go straight a little bit and they will drift off that way. Then, shoot! (this works better if you have good three-point ability)
If you want to dunk, get outside the three-point arch and wait until your man gets on you. Go to the right/left real fast and they will move in that direction. Then, go straight and, well, dunk/layup it! Another one is when you're on M.J. Creating A Legend Mode or My Player Mode, when the other team shoots, run to the opposite goal and when your team gets the rebound request a pass by pressing the A button when you get the ball, keep running and dunk/layup it!