For the first few minutes, they'll be talking.

After that, the three prospective Beaters will mount on their brooms and start trying to bat a Bludger to each other in order. A second Bludger is added to the little game at one point, and then hits start becoming common. Willow's strategy of hitting everything with a bat really fast does mean she's the one who's hit the least and who hits the others the most.