Depends on the subject and how the professor will test you.
If it's a calculus class, for example, and it's meant for science & engineering majors, the professor will most likely present the material in a practical way. Meaning, he/she will go over a lot of examples and the operations will become route and simply mechanistic. Reading dense math textbooks with derivations of equations probably wouldn't be useful for this course. Your best bet is to read the chapter once, and do lots and lots of practice problems.
For chemistry, I just read every chapter we were learning that semester. Read kind of slowly so you don't have to go back and re-read it in the future; try your best to visualize things you are reading, and maybe associating them with other concepts so they will stick in your memory more. For example, when you learn the trends of the periodic tables in chemistry, you learn that as you move down a group and to the left within a period, atomic radius increases. You also learn that for s- and p-block elements, first ionization energy decreases down the group and decreases as you go to the left of a period (opposite of the radii trend). So, you can connect the two concepts by realizing that if the radii of the atoms are increasing, the electron you want to remove (relates to ionization energy) will be easier to take off.
For biology, pretty much just read and re-read until you feel you really have it memorized. Not too many tricks here, except for mnemonics. There was a great list of mnemonic devices for introductory biology material in the MCAT forum, you might want to head over there and check it out.
For history and the like, pretty much just try and get yourself interested in the material. I honestly love history, so reading above and beyond the material never really was a problem for me. Hopefully this helps you out a little. Regardless, you'll find what works for you soon enough.