For the Passing challenge, when a ring turns white, it is about to change to either yellow or green. Use that to see who to shoot it to.
For the Tackle and Shoot, it is best to tackle as soon as you can. When you shoot, look carefully for an open ring. Hold Shoot, then launch.
For the Seeker, hold A until you get close enough. Note: It may be difficult to steer.
For the Beaters and Bludgers, the best way to avoid the Bludgers is to stay either ahead of it or to the side of it so the Beaters can whack it away.
For the Special Moves, use a similar strategy from Tackle and Shoot, except with a Special move.
For the Combos challenge, hold L + R down and keep pressing A as fast as possible to do up to eight combos. Watch out for the Keeper.