I was a polsci major myself. My method for doing well was a combination of a modified Cornell note taking format with flash cards for certain concepts. This was how I obtained a 3.84 my final year in school taking only upper division biology classes concurrent with my pre-reqs. I failed to make A solid in 14/42 credits earning 6 B+ and 8A-. These might have come from the load itself, taking pre-reqs with upper divisions via special permission, or sloppiness in performance on my part. But hey, I got my biomedical science degree with my pol sci so it worked out just fine for me.
Modified Cornell Method: Take printer paper, fold the right corner such that if you folded the left you'd have thirds. Draw a line. The outer section is for either your homework questions or questions you make up based on the notes you took. The top side of the flap is to mark page number, lecture content headings if provided, and formulas. Open your flap. On the right of the line you drew, your notes will go here. This will enable you to backwards engineer the questions you would anticipate in biology if you are meticulous about making questions based on your notes. In terms of chemistry and physics, this method works as a good way of working out sample problems and being able to revisit them later because the solution is under the flap and provides a working example when you are studying. These are great to reuse when prepping for the MCAT, PCAT, or DAT.
I used flashcards for stuff like developmental biology, diversity of life, ecology, differentiating SN1/2 or E1/2, generalized reaction rules, named reactions, orbital stuff, specifics about obtaining certain isomers, really anything that seems convenient to be able to mentally recite.
If your professor provides the power point in advance, it's nice to do 3 slides on the left, notes on the right of each slide. Still bring blank paper in case of diagrams or for problem solving.
I didn't take the MCAT but I got a 23TS (composite score made of gchem, ochem, bio) on the DAT which in 2009 was a 98.3%ile (when I took the DAT, it no longer provided percentiles). Given the way the scores have been edging up it's probably a 97th or so now. If you take the MCAT close to your pre-reqs, you probably won't need to dedicate 8 weeks to studying to do well. You can probably get away with doing one test section per day and once in a while take the full test for a feel of the timing in the weeks leading up to the MCAT.