I have never had to do extended overnight work (meaning everyday). Set some strict rules in regard to waking up and sleeping don't let your friends suck you into drastically changing your schedual, if you have a child...well good luck. Don't become a caffine addict if you are not already. Force yourself to take breaks and get up and walk around (stairs are great). Put something visually interesting about 6 inches next to your screen and farther back it will keep your eyes adjusting and help keep you from getting bleary eye'd (I use SI's swimsuit calender) <img src="/images/graemlins/grin.gif" alt="" /> Drink water for 2 reasons, one its good for you plus the more bathroom breaks the better, use the bathroom on another floor if you can (take the stairs). If you are going to be working in a cube (which you most certainly are) get a mirror so you can see behind you.

Some other things I do -
plant: oxygen is good, even if you're a plant assassin like me..just keep replacing them <img src="/images/graemlins/confused.gif" alt="" />
Fan: oxygen is good, I have one of those cheap desk fans to keep the air moving around me, and no computer chasis fans and CPU fans don't count
Radio: just keep it on very-low playing whatever music you like
Food: eat properly i.e. not pepperoni hotpockets 3x a day, fruit/veggies are your friend
Water: keep the largest bottle of water at your desk you can, shotguning Red Bull and coffee will not help in the long run

Like everything else, take care of your body and it will take care of you