I have been reading though this thread, lots of good, and interesting things in here.
I thought I would mention a few, if I may...
First, I am in the Air Force, so, a few differences, and I was brought in with my commission already in place before going to OTS (same thing as OCS) for commissioned officers it is significantly shorter, but we have to gain all the same information, and do all the same things. My class had just shy of 270 people in it. One thing I can tell you is that you DO want to stand out, but you want to do it in the right way! First, I got there and did everything I could to be put in the highest position I could. I ended up being the Squadron Commander over 80 other OTS classmates. It took a lot of extra work over and above what I already had to do, however, it also have a lot of extra perks. They gave me a little more time to accomplish the things I had to do. Also I ended up getting a letter put into my personal file stating that I was the best Squadron Commander my boss had ever had, which is nice if you want to be considered for a job that is hard to get, like fighter pilot.
Second, I agree that if you work hard you can make it, just do not be a wuss, do not give up. The entire class and the entire staff had a day (near the end) that we competed against everyone else. The person who did the most sit-ups was a female nurse, she did over 430. The second runner up was a Female staff member who did about 420. Do not sell yourself short just based on gender, females are every bit as capable as males! Physicality is only one very small part of OTS/OCS, the smarts to do well is also very important.
The biggest and best advice I got before I went was simple.
You are going to fail! Everyone fails! The system is disigned to be certain that you fail! They know this, they want this, they do not care if you fail! They care HOW you REACT to failure. I.E. If you get all mad about it the DI will be on you like white on rice, if you just take it, accept it, and make no excuses, the DI will have nothing to pick on you about and they will leave you alone for the most part. Do not fear messing things up while you are there, just get over it, move on, and when you are in my shoes you may miss it like I still do.
Good luck, and God Bless!