I found a lot of what I learned at SG was still relevant at Higher. If not in content then definitely in the skills we learned.
I haven't done chemistry or maths since SG and never took physics, so I can't recommend anything specific. ^^; But for other subjects I mostly read over the basics, anything I thought would come up the next year and I re-read old essays paying attention not to the content of them but rather how they were answered.
Most of my friends in school claimed that history was their most demanding Higher - not because recalling information was difficult but because of the amount that needed to be written to get the marks. I didn't take it past SG myself so can't say whether or not I'd agree with that.