This is incredibly subjective, as in so subjective that real world experience is largely worthless. Think of who your target audience is, think of the message you want to send them, write your story to reflect this.
Is it a harsh regime, with impossible challenges to be met each and every day, with no rewards and unjust discipline? The kind that has washouts or casualties as an hourly occurrence? If so, I'd recommend Starship Troopers (Film and book, two very different perspectives) for inspiration. Of course there's also Full Metal Jacket for a real taste of bastardisation. :)
Is it a reasonably humane regime, with serious challenges and just rewards/discipline? Is military service desirable for one reason or another? If so then Starship Troopers (Book only this time) and the Frontlines novel Terms of Enlistment are good examples, as is the aforementioned Old Mans War.
If the regime goes beyond harsh, into dehumanising, then look no further than the movie Soldier, starring Kurt Russell.
Ultimately, for a squid, recruit school was pretty easy. There were some serious key points there though that most literature tends to gloss over, we don't think of them much either. It's all about mindset, and if you approach it that way things will make sense.
The very first week of training is pure shock, your old life is torn down with things as simple as rigidly structured meal, bath, bed times. We'd get up every morning at 0430, wakey wakey was piped at 0450 with PT at 0500, but only the first week recruits were in bed for wakey wakey. PT would be followed by rapid showers and dressing, with the entire school fallen in to march off to breakfast at 0610, cleaning stations at 0630. Parade was at 0700, classes started at 0730, usually with drill, sometimes with PT. When moving between 0700 and 1700, we were to be doubling (running in a formed squad). The entire school would form up again for lunch at 1115, back at lessons by 1200. These would carry on until 1700, at which point we could finally head to our blocks, get laundry done and be changed for dinner at 1800, where the school would again form up and march off. After dinner was cleaning stations at 1830, with rounds at 1900. From 1900 to 2200 our time was our own, to wash, iron, polish, relax, socialise at the club. Lights out was piped at 2200, with the block custodian performing a check to ensure we were all in bed.
Discipline is strict, with even small infractions pulled up sternly, no matter how hard you tried, you never got everything right, there was always issues with dress, conduct, attentiveness, knowledge etc, if it could be wrong, something was wrong with it. We couldn't even contact our families or leave recruit school, the Navy was strict about removing all outside contact. This was very deliberate to shear off our old lives, force us to look around us, rather than a thousand kilometres away for our support. Eventually each of us looked within ourselves and asked "WTF did I just get into?" For me it all manifested after the first week and a half, and I don't mind admitting that I broke down, but I formed lasting friendships with several of the others in my division.
After the shock wore off, recruit school ground on, intense physical exercise, constant running, push ups for nearly any error, most of the exercise was in the morning with classroom learning in the afternoon where many recruits fell asleep and were disciplined. I lost 20kg of hard earned weight in the three months of recruit school. All muscle gained in the gym and playing hockey including representing my state, I was less than impressed.
Pretty quickly we learned not to ask any questions, just do what the instructors told us to do and keep up with the team. It almost pains me to admit it, but I had great fun once I'd gotten over the shock, I'd found a life I didn't even realise I wanted. After four weeks we were allowed our first weekend leave, where we could head off into the nearest city and drink and be merry. We already had two pays built up (A pitiful amount of money, recruits are paid next to nothing), but we all managed to spend all of it in our own way. From that weekend on there as a textural? change, not sure how to phrase it, but we'd settled down to the grind and were now enjoying it. Discipline was still strict but largely self, rather than instructor, applied. The physical aspects hadn't gotten any harder, as the bar was set high on entry and kept there. The classroom aspects remained largely simplistic, although the training about battlefields and natural disasters was fairly horrid, seeing graphic images of people killed on the fields of battle or in typhoons wasn't pleasant.
On the whole, we were comfortable with the routine of getting up at 0430, PT at 0500, breakfast at 0630, parade at 0700 and so on. We'd all realised that we were going to make it, those of us that wished to leave did so at day 70, by week eight the rest were going to graduate, nothing could stop that now. This lead to a relaxed and somewhat festive mood, for pretty much the last month. Everything was easy now, our bodies had reshaped themselves, the civilian had been beaten out of us. We couldn't wait to move on to our initial employment training and start actually learning about our future jobs. It wasn't the night before graduation but the entire week, that effectively became one long party, it didn't really register on me just how much the experience had changed me until I went home. I walked into my old room, looked around and decided this wouldn't do, for the next two hours I cleaned and cleaned, with my mother watching on in bemusement, she stepped in when I was heading off with the iron to do my sheets though. I didn't realise that she'd cleaned my room before picking me up from the airport, and she didn't realise what a clean freak recruit school had turned me into.
Hope this helps a bit. :)
