I coach high school teams in both the spring and fall. Having done this for a number of years now, there are definitely a few sins that we have to coach the kids away from on a regular basis. In no particular order:
When the opponents are in the one up-one back formation, hit away from the player at the net. We probably repeat this more than anything else.
Some sluggers like to use those big topspin strokes from the baseline (with lots of net clearance) for doubles because it's what they know from their training. In a doubles setting though, those strokes often leave the ball up around shoulder height and a poaching opponent with some awareness will gobble them up. If they can't keep the ball away from an opponent up at the net, they have to at least keep the ball LOW.
I constantly remind my troops to mind the wind. Chuck a defensive lob up in the air with the wind on your back and that shot will usually fly long. No downwind lobs.
When it's feasible, avoid getting stuck in the one up-one back formation.
Otherwise, I'd say you've covered a lot of the sore spots.