If you could go back to the start of year 12...Watch
I thought that I'd have time over summer to revise over year 12 content, but instead I have to do history NEA work, and year 13 prep, as well as trying to cover year 12 content. So definitely keep ahead on your work
I would've made sure I wrote notes for all my topics and kept everything filed nicely. The amount of sheets you get in year 12 is insane, you need them to be well organised for revision.