If you are going to OATS very soon just brush up on the maths and physics as suggested. If you are not going for some time I'd suggest you get hold of a set of course notes and read them. If you can get some of it to stick now it will help when you are shown it in groundschool (assuming you are going to do it at OATS). If you can get a copy of home study notes they will have all the explainations to problems and concepts. It's all easy enough, it's just the shear volume that you are required to remember that makes it tricky, start now and make life a lot easier.
Good luck
PP