If you go to a school that's really ruthless about labs (I do) here's the story:
1.) Always go over the lab ahead of time--you have to write it out anyway in order to do it--but don't just copy it word for word out of the manual (some TAs deduct for this). Draw out all the data sheets ahead of time so you can just fill them in later.
2.) Go to TA hours before the lab. YOu can usually get an idea what is important. If you have super-TA's (ie Teaching Associates) go to their office hours too, because they'll usually point out what is important, and this is what is on the quiz usually the next week.
3.) Read up in the textbook before hand (ie if you're doing HPLC, look up the chromatography stuff in your text)
4.) Write it up immediately afterwards. Be really anal about your lab notebook as you go along--I use a three color system (black for my pre-write, blue for charts, notes, ect. pre-lab, and red for intra-lab observations and data. This helps, I really do recommend it.
5.) Haunt your TA, go to his/her office hours, they seem to appreciate it when you show that you care.
6.) The quizzes are the hardest part (here anyway, but I think this is the same anywhere). Consult multiple textbooks, because the quizzes usually test minutiae. Know lab lecture notes and manual details inside and out. Do all practice problems. Try to do as many practice problems as possible before the lab and ask questions during the lab that help you answer these questions.
7.) PICK A GOOD LAB PARTNER! If you go somewhere where there are a lot of postbaccs in the class, always work with a postbacc (even if you're an undergrad) we always prepare well, if anything to a fault. Also, in group-style labs (for example HPLC which you do in a group of 8 or so) the older post-baccs will usually take over the lab and try to impress the TA. Free-load off of them; you'll look like a gunner just by association (and TA's like hardworking students, just never bitch about your grade and look like a gunner). If you're a postbacc, don't work with undergrads--they have other classes to worry about, go out during the week and don't prepare for the labs, etc.--I've seen undergrads doing their writeup during lecture, which I totally understand (because I too, was once 18) but you want somebody who can fill in whatever you don't know, so go with the must gunerish person possible.
Sounds pretty gunneresque, but anybody who's done GChem lab here knows that that's the minimum to make a B+. To get the A, you really have to ace the quizzes, which means lots of outside research.
Good luck.
Edit:
Additional note: 8.) Remember all those ridiculous "250" canvas bags we got during orientation? Put your lab coat, goggles, combination lock, and drawer keys in one and use it just for lab, that way you'll never forget any of you things.
