Go through all your tests and take a note of every single mistake you made, then label them depending on whether they were silly mistakes, small mistakes, or just because you didn't know something. When you're revising, go over these things first and do lots of practice questions until you're getting full marks on those questions without too much difficulty (really recommend revision workbooks so that you can save past papers to later in the year). Start with the things that you just didn't know and work down the chain before starting to briefly go over the things that you understood to start with. I'd do this topic-by-topic myself. If there are things (e.g. symbol equations, converting decimals) that come up in multiple topics but you can't seem to do right, go and see your teacher for extra help with those things.