A great drill to do with our coach or with a friend.

Put some cones/targets down on the diagonals, both deep.

Then, if your working with a friend get him to start on the far baseline and you feed him a deep ball- he returns cross court- you feed a mid court ball- he once again hits cross- and then you feed a forehand/backhand volley and then smash, he must continue to hit cross court.

Then he goes back and does the same but on the other diagional.

Below is the set up for a group practice, but I like the idea of one to one for this.
Click on the diagram below to zoom.