In reply to Calder:
Yep, that's always a useful conversation to have. Also worth begging them to *please* point out mistakes as you're making them during sessions - it's human nature not to be too critical of your mates but constructive criticism is so important.
Other drills might include:
Climbing with straight arms.
Leading with your feet (concentrate on bringing feet up first and moving the hands when the holds are in comfortable reach, rather than stretching yourself out for a hold and then bringing the feet up after)
Trying to move your body position so that you always de-weight the hand you're going to move before you move it (rather than going dynamically)
Or the opposite of course, drilling loads of deadpoints.
Flagging - try to eliminate foot swaps by flagging instead, or climb with one foot, just flagging with the other (so you can press it against the wall to eliminate barndooring, but no smearing or downwards pressure on holds).
Basically, just pick any element of technique and try to find a way to concentrate on that for the session