A few notes from a 10-weeker:
Ten weeks is a long time, and there's hardly any downtime to heal, so whatever chronic injuries you have, get them taken care of, and ease off your workout schedule the week before you ship to reduce the risk of injury.
The 10-weekers were allowed to DOR prior to pickup (categorized officially as I(nital)DOR). One candidate did so when I was there. Don't do it. You haven't seen anything yet. Tough it out four weeks and then decide if it's right for you.
Put out on the PFT, because if you fail it (or any of the events), you'll be put on platoon probation off the bat. You can get by with borderline pullups and crunches, but failing the run will skyline you. By our intermediate PFT, 22:30 was the slowest time (mine). Colonel Rachal told me when I got boarded that while some candidates who arrive at OCS with a borderline run time (24 min is the minimum, my initial was 24:01) make it to graduation, most don't. Get that run time down.
(A brief aside: Probation in a nutshell):
If you fail a certain number of graded events, you'll automatically be put on some level of probation. You can also be placed there for various offences such as consistently lacking bearing. You really have to be a screwup for the latter to happen, most people got placed for event failures.
Platoon probation has no consequences, you'll just be watched more closely.
Company probation limits your liberty to Quantico Base, but you're still allowed to go to the PX and Q-town.
Battalion probation limits your liberty to Brown field. This really sucks, because if there's anything you need that the OCS PX doesn't have, you'll have to get your platoon-mates to do your shopping for you.
I was on Battalion probation... you don't want to be on it. You never get taken off probation once you're on it, so take that as a strong incentive not to fail anything.
(aside over)
Pay close attention when your Company and Platoon staff are introduced - take their name and rank down if you can. Pickup was crazy. I've blocked most of it from my mind (I saw photos of my platoon during pickup and I'm thinking .... I don't remember that). The only thing I would say is to keep your cool, move fast, and help your platoonmates. The routine varies by platoon and company staff, so what one guy did may not be what your platoon will do. For example, I had all my stuff in ziplocks in preparation for the seabag drag. It never happened. Instead, we came inside, dumped our stuff in our lockers, and spent an hour producing items on demand "get X...15, 14, 13....2 BACK ON LINE 1 DONE STAFF SERGEANT." Those of us with our meticulously packed ziplocks ended up ripping them apart and dumping the contents in our footlocker to find whatever it was we needed. Adapt, and think on your feet.
Like the original poster, I don't remember much from the first two weeks. The staff told us what to do and we did it.... fast. Whatever you do, don't let you platoon mates hang out to dry. Somebody missing a cover? Lend them yours. If somebody screws up, they will ask the candidates to his left and right (and later, his fire team and squad leader) why they didn't notice and correct him, and occasionally they will punish his neighbors/superiors as well.
Most of my platoon admitted to having doubts about being there during those first days after pickup, because it is utter suckitude. I know I did, and I was was pretty locked-on mentally. It'll pass. Like klostman said, this isn't how the real USMC functions. My OSO came by and told me, hey, we never treated you like that at the office. It's just a phase you have to go through, for them to see that you can function under the stress of combat. They can't start shooting at you, so the have to resort to playing mind games and screaming very loud to simulate that level of stress and chaos. Remember that. The games and mental abuse will ease up over the weeks, especially after week 4 and the first wave of DOR's, and as the candidate billet holders begin to exercise their authority.
Whatever you do, DON'T EVER GIVE UP. It will be physically rough, but if you were selected, you have the ability to make it. Getting through the runs and humps is to a large degree mental. I had a great deal of trouble physically; I didn't pass a PFT until a month before I shipped, and failed my initial run by 1 second. About three weeks in, after getting placed on Company probation for straggling on runs and getting dropped from our first hike (Da Nang hill killed me), I realized I should have taken more time to prepare. But here I was at OCS, and I knew I couldn't DOR, or stop giving 100%, because if that happened I'd never get a chance to come back.
I was sent before the Colonel in the fifth week. With me was another candidate who'd caught pneumonia and missed a good deal of training.
The XO walked by as we were waiting and asked all of us waiting for the board if we wanted to be here. Most of us sounded off "YES SIR" unhesitatingly. He mumbled some stuff about "this summer is basically shot, but this candidate would like to return next summer". He was dropped and wasn't given the opportunity to reapply, because he gave up.
No matter how badly you think you are doing, the decision to drop you is the Colonel's, not yours. The attitude of "it's going rough, so I'll quit and try again next summer" is not what they're looking for.
SOUND OFF. Don't be they guy lip-synching. They will catch you, and your platoon mates will hate you for it when the PTI makes you do pushups for not being loud enough. Besides, as other posters have mentioned, it's fun. Moreover, it's good practice for when you have an enlisted billet and have to do some screaming of your own (everything is done for a purpose at OCS). I lost my voice the day after pickup from all the screaming we did, and quickly learned how to drop to a lower pitch like the SI's did so they could still shout(if you pay attention, they lose their voices too). I sounded like a damn frog, but I kept my volume. When it came time for me to be Cand. Platoon Sergeant, sure, I lost my voice, but I could still shout orders. Don't be the candidate squeaking out orders to the platoon (or worse, the company) because they never figured out that trick.
One big problem my platoon had was "too many Chiefs, not enough Indians." Everyone wanted to show off how good a leader they were, so naturally everyone contributed their 2 cents on how **** should be done. All that leads to is disorder and chaos. We had a couple of guys get chewed out for doing stuff they weren't supposed to (like shaving at the wrong time), because some non-billet holder shouted out a suggestion that they, in the confusion, took as an order from the chain of command. If you aren't in a billet, shut up and follow the chain of command. Pass suggestions up the chain, and in the meantime, listen to your billet holders, no matter how much you may disagree with them. When we finally figured this out around week 5, things went a lot smoother.
You will get sick. By the second week everybody had a nasty cough, and three guys in my platoon ended up with pneumonia (two ended up dropping, but the third is still there as of week 9 despite two weeks on bedrest/light duty - show them you want to be there and they'll keep you around). Use that hand sanitizer often, and bring it with you when you go out to the field.
Yea, I miss OCS, partly because I got NPQ'd and my platoon is a week from graduation.