This is what our teacher told me.
He said that on my first read through i should chuck in a sticky note etc. at any point i find ANYTHING at all interesting. whether it be a description of a character, landscape; whether it be a revealing passage about a certain character etc.
After my first read of a novel he said i should then go through and read from as many outside sources on that novel i could. Study guides, wiki, spark notes etc. and then get a feel at what the themes of the book are. what essay questions on the book are most likely to be based on etc.
Then i should re-read the book again with this in mind, and again, make note of what i think is important.
My teacher also told me that it is these initial readings of the stories over the holidays and early in the year that are quite important as you formulate your own personal opinions on the novels, and in return you form your own opinion about what is important and what is not in the novel before you are flooded with materials and opinions of teachers and whatever; and usually it is during this initial period where people can pickup on unique ideas and phrases etc. that separate you from the rest of your cohort when writing essays.