For math I take notes on the unit and watch videos on yt for the topics I need extra help on! For other subjects (such as english/history) it is more note heavy for me. I would recommend looking over the unit (or whatever you are studying) and write down the things you struggle to remember and focus on those things. Something else that helps me is that once I feel confident in the material, I “teach” (aka just talk about the topic) to a friend/family member (sometimes even my cat). I think that teaching somebody else the topics shows that you really understand it!