Press A or + to pass the ball, wiggle the remote back-and-forth / up-and-down to dribble, press B to get in to position, thrust the remote up to jump, and in midair flick your wrist towards your TV to shoot.
Flick your wrist downward sharply when the defender is dribbling to steal, and flick the remote upward sharply to block a shot (HINT: IF YOU PRESS B WHILE YOU TRY TO BLOCK YOU COME UP FASTER!)
If the defender (you or the computer) tries to steal and misses, their Mii will paw at the air, or fall flat on their face. The ProClass opponents often take advantage of you and shoot right when you're down (this is when my hint comes in handy).
There are several areas in the court: the dunking floor, the layup lanes on either side of them, the foul line, the two-point line and the three-point line. If you dribble past the defenders into the blue dunking floor, you can dunk. The lighter blue layup lanes are dunkable, too. If you dunk from either layup lane, you will dunk with one hand (if you selected right-handed, the Mii will dunk with their right hand, and if you selected left-handed, your Mii will dunk with their left hand. You can figure out if CPU Miis are right or left-handed by which hand they dunk with. On the dunking floor the Miis will dunk with both hands. On the first basketball team you will encounter, Miguel is right-handed, Anna and Takashi are left-handed. On the champion's team, Eva and Tommy are right-handed, but Tyrone is left-handed.
HOW TO DUNK: Dribble past the defenders to the layup lanes or dunking floor, and press B to jump up. Flick your wrist downward when your Mii is right over the basket to dunk. Sometimes your Mii will just let go of the ball when it's over the rim, but sometimes they grab onto the rim and pull the hoop down with them. Dunking and shooting from the two-point line is 2 points, and shooting from behind the three-point line is 3 points.