I willl echo and expand on several suggestions already made.
1) Buoyancy control. I know you asked for suggestions 'apart from buoyancy control'. But, I would add to the 'front end' of buoyancy control - proper weighting, which is critical to good buoyancy control. Determine the proper weight, FOR YOU, in salt water, using whatever exposure suit you will regularly dive. I would then add to the 'back end' of buoyancy control - work to be able to control your depth with your breathing alone. Certainly, you may use you BCD with major depth chanes. But, work to develop the ability to control your movement in a 5-10 ft vertical plane using only your breathing. You can do it if you are properly weighted.
2) Trim control. Are you truly horizontal in the water? Or, like many divers, do you swim at a 30-45 degree head-up angle? If 'cleanliness is next to godliness', then trim control is next to buoyancy control.
3) Finning techniques. Can you perform a frog kick, efficinely, effectively, and effortlessly? If not, work on the frog kick during Christmas. If you have a good frog kick, watch the YouTube videos and work on a back kick. And, once you can do that, start working on helicopter turns, performed WITHOUT YOUR HANDS (see #4).
4) Danglies. One of the more common and needless 'danglies' are hands. Most of us don't realize wthat we use them as much as we do. So, work on executing an entire dive withyour hands clasped lightly and comfortably in front of you, and DO NOT use them except for a) adding air to your BCD during the descent, b) purging air from your BCD during the ascent, and c) clearing you ears (and, then, only if you pinch your nose to do so).
5) If 'a picture is worth a thousand words', then a moving picture (aka video) is worth even more. Find someone to watch you lead a dive, as suggested, and make comments. Even better, find someone to do that AND take video footage of you in the water while you dive, so you can see what you really look like. Most of us are surprised by what we see.