Depends what unit you get put into, artillery, infantry and so on. Infantry is usually the toughest one physically. I'd try and get out on medical condition. Just bug the doctors a lot about it and keep telling everyone your knee hurts (which most likely it will). If you're persistent enough you'll usually get transfered to an easier spot (a lot of people do that with no medical issues whatsoever and succeed nonetheless).
While you're there expect a lot of shouting, useless orders (they give the stupidest orders just to train you to obey thoughtlessly), a lot of walking and carrying (2-10kg equipment), quite enough of sleep deprivation (about 6 hours of sleep per day, sometimes less).
First couple of weeks are usually introduction and will be a bit easier, it will get harder as it goes.
Then there will be a whole lot of time spent at the shooting range (about a month) which is rather shitty because shooting ranges are usually off base and you get back to base only on weekends (meaning no shower for almost a week and sleeping in tents that leak in winter and are scorching hot in summer), also since you're off base there's constant need for guards (that includes night time, meaning another cut of 10-30 minutes out of your sleep time, which sucks even more if its in the middle since you won't be able to fall asleep right away, basically cutting 6 hours of sleep into 5 hours of sleep - try and get either the first shift or the last shift).
If you get into infantry the shooting range will continue for another couple of months (this reminds me, get some pads for your knees and elbows, its a ***** falling with them on the concrete floor of the shooting range, this also reminds me - you'll be getting a lot of cuts and bruises, so brings some liquid soap and bandages for first aid, it could take a day till you see a medic and a week till you see an actual doctor). Bring warm clothes for winter, and a sports outfit - chances are you'll have running exercises.
If you get into artillery/tanks/etc the next couple of months will be spent learning about the vehicle and your job operating it (which is frankly much simpler than the shooting range).
General tips - try to blend in (stand in the middle and chances are your superiors are less likely to notice you), shit and piss whenever possible (i'm serious here, get used to the idea your time is no longer your own and the most basic actions now require permission from someone else who probably doesn't care about soldier number xyz and his weak bladder, which also reminds me TP is worth its weight in gold in the army so bring 2-3 rolls as backup), try and make your orders in time but don't exert yourself too much (there will always be another task for you to do when you finish your current one, it will be so for months), any problem you encounter - immediately let your superiors know repeatedly (noone cares about you if you aren't loud about it), stay organized as much as possible - be prepared to get your clothes on in complete darkness (chances are you'll either be woken up in the middle of the night for a guard shift or before sunrise as your daily routine) it will save you much valuable time.
Never forget where your weapon is - this is a major offense in the army that will get you screwed over, sleep with your weapon beneath your head (yes, i'm serious, if you don't your superiors will try and steal it from you in the night and come morning punish you for it). Bring some soup or candy with you, most army food is atrocious and monotone. Make sure you check your uniform and boots right after you get them - they are usually the wrong size or otherwise unusable, make sure you get all the equipment you signed for - you'll have to pay out of your "salary" for everything missing once you return it. Bring a lock with you - to put on your bags, when people lose their equipment they steal it from their neighbours. Bring a marker and write your name and serial number on every piece of equipment you get - in case of dispute you can prove its yours.
Bring a knife - both to cut food in the field and for some other stuff (believe me its very handy). Bring scissors to cut your fingernails, bring a lighter - again it can be very handy. Bring a flashlight - for obvious reasons. Bring something antifungal - your legs will thank you for it. Bring a pen and a small notepad - good for writing down lists of equipment, things you might ask from your superiors, your tasks and so on. A week long supply of clean underwear, shirts, socks (though those might be provided). Bring some footwear for showers - might save you some fungus problems in the future (and don't forget a towel, shampoo and soap).
If you get into basic training for non-active combatants it will be a hell of a lot easier both physically and discipline-wise. I suggest you get as far away from air and water branches and stick to ground - those guys don't usually see home for quite some time.
Ofcourse this nightmare called basic training only lasts a few months, then it gets easier in many aspects and harder in some others. Despite everything i mentioned, it might not be THAT bad, you might actually have some fun and meet some nice people (though unlikely...yeah i'm an optimist). Its been a few years since i got out, so i may be a bit off (not to mention every experience is unique).
There's was only a guy or two out of thousands at my base who commited suicide, so that's unlikely to happen to you (though not impossible) - if you ever feel like you are about to - please don't and tell your superiors you need to see a psychiatrist and refuse to do anything untill then (the worst they can do is send you to prison, which in all honesty is actually better in many ways).
And the reserve duty after you get out is really not that bad in comparison.
Master Sergeant in reserve Knife.
