A few that have worked over time:

1) Stop at the top drill. Get to the top of the back swing and have the student hold for 3 to 5 seconds. Then initiate the forward swing. This gives great feedback on what they are doing and then we can correct and give them the proper sequence. 2) Obstacles. Basically putting road blocks in place to help create a better swing path. 3) Feel as though your trail elbow is under your lead elbow approaching impact. This is a good one for players that have a decent lower body movement and the issue is more upper body oriented.