If you're getting bad results in your mocks your first priority is to work out what went wrong. Did you make silly mistakes? Did you phrase something incorrectly? Was it that you didn't understand? Did you not know your facts?
Page by page, go through the revision guide and consolidate each idea/concept with the textbook and your own notes. Make sure you understand every idea and fill in gaps in your knowledge. On each page, you want to do this:
1) UNDERSTAND. Make sure you could explain each concept to a five-year-old, you understand it so well.
2) MEMORISE. Add facts and definitions to your knowledge. This bit is difficult but you can use flashcards, mind maps, etc.
3) APPLY. Do practice questions on the topic, and get your exam technique down.
Hope this helps! X