I typed up my autobiography on computer and then transcribed it by hand. I heard that they sometimes like to collect the papers and then make everyone redo them so I kept the typed version in my pocket. (and hoped that they wouldn't think to ask for that one) They asked for the autobiography, I handed it to them I only saw it one other time during the "getting to know you meeting" with my section leader.
With that said, there were people who had to rewrite their autobiography 5+ times. Sometimes for sloppy handwriting, othertimes for missing key information. The rest, putting in things that don't belong. "Well that is everything about me but I read that I need 500 words so I guess I will continue to talk about the paper oh wait, there, 500" <-- unacceptable
I was given a few tips (okay I badgered anyone who'd ever gone to boot camp until I knew every little detail I could) including info on writing the autobiography.
Grey is good, save outstanding for later in the course. I was told not to ever tell them more than they requested, for example the languages I speak - and even then play it down. (Writing in the autobiography "I speak more languages than the UN and I'm going to outrank you in a year" is a bad idea.) I know it sounds strange not to be advised to "impress". My experience was that they were far to busy with the guys who were giving them grief to hand out cookies to the keener's. I've found it easy to simply not be noticed, without a reason most of the staff will simply slide on by you with only passing intrest.
My autobiography is 550 words of pure pablum. Everything they asked for, exactly as they asked for it written in a way that gives away nothing else. I'm thinking they have to read at least 10 of these, if mine is uninteresting - raising no red flags, it is one less thing to deal with when I'm rushing around.
Just the advice I've been given with my personal observations. I've said it before, I'll say it here - enjoy it, this is the fun part.