For biology I found that my notes in class would have a lot of gaps in them and so afterwards I used the textbook to make sure they were full but also concise, long notes aren't as helpful. From this I made flashcards so I could continually practice facts and any formulas I needed.
For chemistry, I used a similar technique and used chemguide and chemrevise to ensure my notes were concise and then, again, made flashcards. If I didn't understand a topic from class and these notes then I would watch E.Rintoul videos on youtube. I also found diagrams to be great for learning mechanisms and practicals.
For both however the most important revision technique is doing past papers and past questions of all types. Just keep going over them and getting used to what they want you to say and how they word questions. They're also a lot of application these days so past paper practice is more important than ever!
Hope I've helped and anymore questions just ask!