As a recent graduate of PLC Seniors, and previously PLC Juniors. I would say the best general advice is this: Always move fast and sound off (yelling at top of lungs), and if you finish first (tasks in squadbay, playing games, etc) help fellow candidates.
Use common sense when in any authoritative position (billet) you are under stress, but not so much that you have to freak out and start "blue-falconing" your fellow candidates.
OCS is a rite-o-passage for us wanna-be's and you have to take it at just that, a right of passage to see if you got it mentally, physically and psychologically. Try to get some study gouge from other candidates that have been through it. General orders is a start. Look into some basic history, M-16A2 specs, basic marching/drill, fire-team tactics/formations.
If you go physically prepared i.e. run a 3mi from 20-23 minutes, ...atleast 15 pull-ups, and 85 easy crunches you should be good to go...this is definitely a first class PFT and the less you have to worry. If you have no problem running, PT'ing, you spend that much more time focusing on other stuff. I'm just saying be able to PT, run, all that good trash and you'll be straight.
Read other threads and posts and you'll get a better bearing on what you need.