Well, firstly I would set up one section if notes for each of the following sections: characters, themes, worlds/environments/settings, structure, symbols, author's voice/intentions/purposes.
Then within each of these, divide the section into the relevant topics (so for characters: john, kathy...etc, for themes: truth/knoweldge/secrets/mystery/nature of evil/love etc...).
Once you've set that up, I recommend filling each section with a mix of quotes, ideas, key sentences that your teach may have said, really anything that you think relates to that section. Then, when it comes to writing essays, you can look in the relevant section and you've got a whole heap of quotes, ideas, key words, possible topics sentences, related events in the novel etc.
Well, thats what I'm doing anyway...