i take notes from textbooks, review books, other sources and consolidate them with lecture notes into one written/typed document. it's time-consuming at first, but come exam time, it saves me time in frantically flipping back and forth from piles of different references. i'll also have a permanent easily accessible source for future review.
Im not really efficient at studying these days. Sometimes it can hurt me some.
But I usually try and make notes in my handouts and whatever I read. Sometimes I'll transfer those notes to another piece of paper, or try and make questions to those notes.
And right before exam time, I try and consolidate my notes on a few sheets of paper writing really really really small. Wish I could do it earlier (ie right after the class) but sometimes I can't really take out the pertinent info just then. Its not till the end that things begin to come together.
1.) Go to lecture.
2.) Read the text.
3.) Read the relevant review books.
4.) Repeat steps 2 and 3 ad infinitum.
After a few months of school, I realized that I never really learned how to study. Just slogging along and reading the same crap a million times works the best for me. I can't get into writing things down or making charts or pretty pictures.