RANT - a useful tool to get your head around what the needles will do in the hold, procedure etc. It has various tutorials to give you a heads up on the principles too. Theres more, but a search will show you its been discussed loads already. It was written by a CAA examiner too!
Morse code - Not a requirement to learn anymore, but try to have a better appreciation of it. Learn the idents of the navaids you may use on training/test. Incidently RANT has a Morse tutor too, with a "dummies guide" to learning a few key letters. (F, Q, C, D, etc)
When you start flying, get the airborne checks nailed. If you can rattle them off it will increase yr brain capacity to do other things.
If you can think about the aircraft and setting up navaids properly it will save you a lot of bother. Your instructor should explain this. Keeping thinking whats next!! Good luck