just do your best and hope for the best. for some people (like me), its damn near impossible to get A's in all of your pre-req's. Many times you will study for hours and hours only to barely get a B- while you see first year students set the top of the curve for your class. It can be frustrating and I have still not figured out how to get an A. The best I have done is a B. I started out with 4 C's but have recently gotten nothing lower than a B-. My advice is don't take chem I lightly. It may seem hard at first but it will be the EASIEST pre-req class you will take. so get your A's and B's while the getting is easy.
I am more than half way done with my pre-req's and I have learned to give up 75% of my social life. During midterm weeks and finals, I spend Friday, Sat, and Sun nights studying at the library (yay for 24 hr room). I spend the day sleeping and relaxing but when night time comes, I study until my eyes and brain hurts. I also study an avg of at least 4-5 hrs a week for each subject. When you have an "easy" week with no midterms or tests, TAKE ADVANTAGE! read half the chapters or do 1/3 of the hw.
oh yeah, office hours! professors, TA's, tutors, etc. use them ALL!
and lastly, good luck. because no matter how hard you study, sometimes the difference between an B and a C can be on the professor you take since some are WAY easier than others.
oh yeah, READ THE BOOK and DO as many hw problems as sample tests are u can. I learned that its almost a guaranteed B if you do all that.
FORGOT TO ADD: I got to UC Davis and they offer workshops for science and math courses. basically extra classes!
If your school offers those, take them. It's an extra 2 hrs a week of "studying". basically reiterates lectures and gives us tips. can be boring but in o-chem, theres so much info that any extra help is worth the time.