Helldog- The link that DocT posted is a great site but I would also like to offer you a little about OCS from my perspective. You can take what you want and leave the rest. I was an instructor there before I attended last August so I had the opportunity to see OCS from both perspectives.
First of all, before you attend you want to get as much sleep as possible, even if it means not leaving your bedroom the week before shipping off. Once you get off the bus (or your car) you will have one of the OCS staff members (not a Sergeant Instructor) escorting you at double-time. OCS is all about getting from point A to point B in the shortest amount of time and in an organized fashion. This is why learning drill before hand helps out a lot.
The first few days are long and boring and full of paperwork. It is hard on those who have never left home for an extended period of time. After processing comes the big day, when you are introduced to your new family. Because many schun on anyone who gives away the details of what happens at OCS, especially the first two weeks I will leave it at this; the most important two weeks are the first two weeks. As long as you do what your told, when your told to do so, and with intensity you will not have a problem with it. Most mornings start around 0500 or so and most don't hit the rack until around 0100. The lights are out around 2200 but most have to either write essays, letters home, do laundry, firewatch, prepare uniform for next day, clean squadbay, and/or stretch out as many muscles as you physically can. Sleep deprevation is the killer at OCS if you ask me. Most of the physical tests and classroom exams are not that difficult if you are well prepared and awake. This is not the case at OCS, for the most part you have to do everything on less than 3 hours of sleep. It takes getting used to but if you can make it to the 3rd weekend, the 24 hours off (liberty) will be the best 24 hours of your life. 20 of it will probably be spent sleeping and eating a huge steak at TGI Friday's. Moving from the sleep issue, I would argue that the most important things you can do at OCS is help other candidates out when they are struggling, and eat as much food during chow as possible. Between the PT and hot Virginia summer days, you will need all the carbs you can get. Usually having time to eat your chow is not a problem, the Sergeant Instructors may not care about you, but they would rather make sure you are fed and hydrated instead of filling out medical paperwork on you.
Another factor that I did not see coming going back to OCS was the lack of air conditioning in the tin-can style classrooms. I remember one of our exams was at about 1500 in the afternoon and it was about 102 outside. Inside it was at least 10 degrees higher and you could feel it. I think about 80% of the company fell asleep during the exam. This leads me to my next point...DRINK DRINK DRINK...H2O is the drink of choice at OCS. Sometimes we would all pretend that our canteen of water was a nice tall glass of Sam Adams, it was the best we could do.
The best way to prepare for OCS PT is to run at least 2-3 times a week in boots 3-4 weeks before shipping out. The more broken in your boots are the less chance you have of getting injured. Believe it or not, there were two candidates who were sent home because of blisters...not fun.
My last point for you is to make sure you polish up on your writing skills. (No more or less than 300 words per topic and you have to underline and number every word. Any word less than 4 letters is not considered a word, therefore you will not number it or underline it.) The best way to attack writing essays at OCS (and I know because I had 15 of them!) is to write them in class in between taking notes. The more you can get done in class the better, otherwise you will have very long nights in the head using the light to write your essays. Well I hope this helps...like I mentioned before, there is a lot more to OCS than this...a whole lot more...but the reason why OCS is so successful is because the extra details are not meant to be spoken. The "Unknown" factor is the most important factor.
