i would say that the most important thing is total commitment. i didn't remember anything about chemistry/orgo/physics, so i've had to relearn pretty much all of it. for 90% of the stuff i've seen on the SA & #3, the concept behind why is more important than any specifics - the answer for every single question is on the screen in front of you, you don't have to answer the question, you just have to choose the right option. my undergrad experience was based on memorizing, especially considering most professors will largely tell you what to study for an exam, and exams being on bursts of information instead of all of say physics or orgo overall. if the book (TBR for physics/orgo/chem; EK for bio) isn't synthesizing the idea, check out videos (chad's at coursesaver for physics/chem/orgo; kahn academy for bio). i stopped grading my TBR passages because as much as everyone says learn from your mistakes, it just takes too long to read each answer - instead of understanding why i made a mistake, i just think i got too many wrong, i need to study this section again. the official AAMC material does a great job of telling you what areas you're bad at - you need to study those sections again. don't try to save money now - my undergrad & masters was probably $200k+, but without a good score on this, all that money and those years and thousands of hours isn't getting me out why i went in in the first place, and when i think of it like that, saving $100 on buying used TBR or $50 in skipping chad's videos just doesn't make sense. don't try to cut corners - everyone will make little errors in every exam, and those add up, so if i happen to get a passage in something i'm bad at (for me let's say optics), and i miss 3/6 q's there, that could be the difference between an 11 and a 9. take lots of practice tests - you might suck at standardized tests, but after taking 8 AAMC FL's, and the SA's, and loads of passages in the book, the sucking at standardized tests feeling will dissipate. obviously test anxiety is very real (i'm lucky to have the exact opposite: i studied 3 days for my GRE straight, took a practice test the night before and got 50th-ish percentile in both sections, only to go get 90th percentile on the actual exam), but you can't anticipate what might happen on the day of the real thing, you can only get yourself as familiar with all the subjects and process as possible.
and remember - i haven't even taken this exam yet (i'm only 1 FL in actually...), but just click up to the top of the forum for the "30+ MCAT study habits" thread, and read those when you're bored of studying. as the process moves along, you'll build your own strategy behind what will hopefully be a good score. all my advice won't be any benefit if you are prone to massive panic attacks to the point where you can't breath in actual test situations, but there's really nothing you can do other than study & practice right now to get you where you want to be. if by the 4th FL you aren't getting the scores you want, just build up more of a knowledge base and hone your passage skills in a workbook. that diagnostic you took isn't something i've read anywhere on here is beneficial or worthwhile (and i'm on here a lot...), so throw all that BS out the window and heed the advice that hundreds and maybe even thousands before you have left on this forum. it's not difficult science (this material is so much easier than my masters, and that wasn't even close to a phd), it's just a lot of it at once. and finally, this is going to sound totally insane - i actually enjoy studying for this. after all the time i spent doing stuff that had nothing to do with getting into medical school (like studying for a history exam because it's a required class and holds as much weight in my gpa as something i might actually use) so i could apply to medical school, i'm in the home stretch to the point where i can taste it. compounded with that is the fact i actually understand the basis behind the core sciences finally years later - after getting straight C's in orgo over the course of a year, it feels great to actually understand it and see that it's possible to develop even your worst areas in the course of a couple months. i may never use it again, but there's more to "it" than paying $$$ for an undergrad degree and coming out with paper that qualifies you for a job - the romantic notions of academia > the reality of american universities. the content review is tedious, but understanding the subjects and seeing numerical results has given me steam on top of the fact that without this i couldn't do what i've wanted to do with my life since i was kid. if you actually want to practice medicine, the sweat of 3 months is nothing compared to the rewards of 40 years.
update: just finished aamc #4: 11/12/9 = 32. if i can do this, you can totally do this.