I agree with Hummi C, BBC Bitesize is extremely useful for OCR. I also find it particularly useful to make posters for each of the units, summarizing the key ideas. If it's a poster, you're more likely to go back and look at it.
Past papers are vital, time yourself whilst doing them. If you struggle on a question, keep revising that particular topic and if you still don't understand, I'm sure your Chemistry teacher will be happy to help you.