As mentioned earlier, for math you just write down whatever the prof writes on the overhead projector. When you go back home/to rez you have to put the notes in a binder (that way, you will be more organized and can find your notes easily when you study..you should do this everyday)...when taking math notes, it's a good idea to write down the new section/topic..for example, if the prof starts section 5.2, you should write down 5.2 as the heading.
For physics, just print the lecture notes and add your own notes to them...it's a good idea to write down the solution to the problems presented in class, as well as the solution to the multiple choice quizzes.
For chem, same as physics..
From my experience, I usually end up sleeping/really tired in class if I just sit there and do nothing...just write down anything to keep you awake in class