In my time as a nolifer I've had many various experiences during races, competitions and my own personal goals. I've collected knowledge on the subject through my own experience and by discussing it with other nolifers (being RuneScapers and others). To really explain what we went through in achieving our goals back in the day, I'll describe what we did to be as efficient at what we did as possible. For most people it'll probably just be insanity or obsession, others might recognize some of the things we did from things they've done themselves in the past, and aspiring nolifers may learn a thing or two about the "old school".
First of all, before thinking about doing longer nolifing sessions, you should make sure you are actually good at what you do, or want to do. In RuneScape, there is a certain maximum xp/hour you can achieve, and if you can't maintain max during the regular day time hours, improving that should be your primary concern. Once you've obtained the amount of skill needed to go 100% efficiently for a whole day, you can start working on allnighters and such. But even though you're efficient until midnight or 3 am, your efficiency might drop drastically once you pass your 16th hour of doing whatever you do. Start slowly and work your way up. Then at one point or another, you will be able to do an efficient allnighter, then a 30 hour session, then a doublenighter, then a triplenighter etc. Don't compare yourself to the veterans right away. Don't think you can do 100 hours straight just because your heart is in the right place and some other dude once did it.
Decide what your goal is. Is it to break a record, and so what you need is an all out attack getting it done in one go? Or is it a certain level or amount of xp, requiring a siege style, steady pace from a month to a year? Whatever it is, be aware of what it is you want. "I'll just see where it goes" IS where it goes. No further than those words. No action will ever be put in it. If you don't want something, if you haven't got a goal, then find one. Nolifing is for the one who HAS a goal and who says to himself "****, I want this, and I'm gonna get it, no matter what it takes. No matter how long, no matter how tired I'm gonna be, no matter how dysfunctional my family will think I am, no matter how many friends I don't really care about I'll lose touch with. I'm gonna **** do it".
Which brings me to the next thing. Consider how much you're willing to sacrifice. I can't remember how many people I've spoken with who would like to do well (both in RuneScape and in real life), but complained that they didn't have time. They had school they needed to do homework for, they had a dog they had to walk, they had friends they had to play bowling with and parties and sports and all kinds of stuff. Things most people think they have to do, but in reality, that's the only thing holding them back. No people are blessed with 40 hour days. Time isn't something given to you, it's something you take, something you give yourself in order to do what you want to do. And if partying and doing homework is what you want to do, that's great. Just don't complain about not achieving the same things as people who put in more effort and dedication.
Passion is the key. Not the key to nolifing, but the key to achieving anything in life. Passion will make you look more clearly at what can be sacrificed and what can't. Passion is what will make you do the same **** for a year without breaks, and still crave more. Passion combined with a certain amount of will power and discipline will take you far. Because while passion will make you begin an allnighter, will power is going to take it all the way. After 48 hours up it will be the voice in your ear whispering "keep going, this is nothing, remember what you want, remember what you can do", while the rest of your entire being screams STOP, GO TO BED! I've known a few people I thought had a lot of potential, but all they had was empty ambition. One thing is saying you'll do 400+ hour months and failing, another thing is saying it and never trying. You can have all the best intentions in the world, but without putting some work into it, you won't go anywhere.
Set goals for yourself. Long term goals, monthly goals, weekly, daily, hourly. Personally I liked setting small goals all the time, and then calculating how long it would take to get there with the max xp/hour, and then get it without losing any time at all. Also, in RuneScape, you were automatically logged out if you had been online for six hours without breaks. It was a nice rhythm, playing efficiently for six hours and once you were logged out, you could go to the toilet or eat a snack or whatever you wanted to do, and then go back and do the next six hours. That would prevent lots of small breaks all the time, which would have wasted much more time in the long run. But also set daily goals. Go for whatever you think is the best you could possibly go for, and if you happen to catch up some time or play a little longer, don't hesitate to rise your goal a bit. But you have to kick yourself in the balls if you don't reach your daily goal, because then you didn't work hard enough.
Know your setup and get a routine. Where do you play? What food will you eat? Is it easy to make, do you like eating it, is it stored far away from you? Will there be people around? When will you sleep and for how long? Have you got an alarm clock? Have you got any entertainment prepared? Have you got any "boosters"? Those are just some of the things you have to take into consideration before getting into a nolifing project. This is mostly for the short burst nolifing, long term goals are a bit more flexible. But you have to think about how you're going to do everything. While it's dumb to sit on a wooden chair that will make your *** sore after 30 minutes if you plan on going 50+ hours, sitting in your bed leaning back on a mountain of pillows perhaps isn't the best idea either. You'll need a chair comfortable for sitting on, but bad for sleeping in. Resist the urge to lie down, even if you want to keep playing, you'll fall asleep and you won't know it until you wake up 12 hours later.
Know your food. I've always liked foods high on proteine, I told myself they would automatically help maintaining muscle mass despite the lack of physical activity. Baked beans was a winner when I did most of my nolifing because my budget could barely afford me eating cup noodles every day. 500 grams of more or less tasty food for $1 was a fine deal for me. I drank chocolate milk most of the time though, some sugar and proteine in a tasty drink was better than drinking water all day every day. Drinking soda can't really be recommended, it's bad for your teeth, and it's got way too much sugar and caffeine. It should only be used as a means to stay up a little longer, but once the caffeine has burned out, you'll end up more tired than you would have been without it in the first place. Energy drinks such as monster, hustler, x-ray and redbull are the same, just in a more extreme version. I was at some LAN get-togethers for RuneScape players back in the day, and the first time we met, we drank only redbull for three days. My stomach has never felt so messed up. As a short time booster, though, it's great. What I usually did when doing 30-50 hour sessions was to drink regular soda (mostly coke) the first 24 hours, then cheap energy drinks such as hustler and x-ray until I'd be really tired, then I'd switch to redbull the rest of the way.
Some people like drinking a lot of milk. Milk is nice, but it's crap for nolifing. The reason parents give their children a glass of milk before sleep is because it contains an enzyme that releases whatever it is in your body that makes you feel tired. I can't remember what the enzyme is called, but I rememer I found it quite funny since the longest I've been awake in one go was done on milk and baked beans.
Also, don't eat high fat foods. While you need energy, don't get it from fat. It will make you unhealthy and tired the same way as sugar. And as a final note on this, don't eat candy.
Dress appropriately. Your body burns off a lot more energy while being awake than it does sleeping, so you will need the energy you have for staying awake. Not for keeping warm. Put on clothes so you'll stay warm during the night, if it's uncomfortable during the day then take some of it off. You're not supposed to feel like an eskimo in Africa, but you should be on the good side of warm.
It's also good for your blood circulation to be warm. I remember nolifing at a friend's house in october, and he had no heaters on at all. We were jokingly saying if he wanted to thaw anything, he'd have to put it in the fridge. However, after 48 hours my calf muscles were at least 50% bigger than usual, hard as rock and extremely painful to walk around with. Gravity forces the blood down into your legs, and without physical activity, your heart won't pump the blood around hard enough to get it up again. Had it been a bit warmer in his apartment, it wouldn't have happened.
Adapt to how your family and friends behave. If your family brings you food and tells you you're doing a good job and encourages you, you might want to stick around. If they are the opposite, and try sabotaging your gains however possible and are always discouraging you, you might want to put some distance to them. If your friends always call you and want to go out and so on, pull the plug and turn it off. It doesn't help achieving your goals to be constantly put down.
Know your own sleeping habits. There are two kinds of nolifers, the ones who can go on forever with just a little sleep every night, and the ones who do killer sessions and then crash for 12+ hours afterwards. Most people have jobs or school or whatever that forces them to be the first option, so you'll just have to do your best with that. Push yourself into sleeping that little bit less every day, and perhaps do a weekly allnighter every friday or saturday.
If you're the other kind, you usually haven't got a problem staying up for a long time, your problem is getting back up. Set an alarm clock and get out of bed. Be realistic about how little sleep you need, you can't only sleep four hours after a doublenighter and then keep going. But sleeping until you wake up by yourself will waste a lot of time.
You also have to make sure your alarm clock actually can wake you up. In my early nolifing days I'd put my regular alarm clock in the opposite side of the room, but after a while I got so used to it I pretty much sleepwalked to it, turned it off and went back to bed. Then I'd wake up 5-6 hours later thinking it didn't ring at all. I ended up getting a special alarm clock in which I had to complete a memory game with four coloured buttons before it would stop. By then it would have woken me up.
Personally I am definitely the kind who stays up for a long time and then crashes. I tried playing 18-19 hours per day with 5-6 hours sleep, but I would end up too wasted to go on. I did 24-36 hours most of the time, and then slept 8-10 hours. Know yourself and then make the best of it. It might be possible to change your sleeping habits, but it won't be easy.
Also, know what kind of entertainment you like, and when you like it. I would usually just watch movies for the first 12 hours or so, then listen to quiet music for a while, then end up listening to metal and trance music. After a while, though, I'd just turn it off to give the ears a rest. I watched all Friday the 13th movies during an allnighter. Pretty bad movies, but they had enough suspense to keep me awake for a little while. A guy once told me he would watch porn while nolifing. I haven't tried it myself, but I guess it might keep your brain turned on for a while. You just have to figure out what works for you.
Mind your eyes. They're the first thing that will tell you you're tired, even if you really aren't. You may have forgotten to blink enough so they've dried out, or your computer's light settings have been too high. Don't turn off all the light though, because then you'll end up falling asleep too easily. I guess if you could turn it into a habit to only open your eyes half they wouldn't dry out nearly as quickly and then at least you wouldn't have to deal with that. But once again, figure out what works for you. Also be aware that even though your eyes are completely dried out and it almost hurts opening them, perhaps you just have dry eyes without being tired at all. If your hands aren't shaking, your face isn't less than 20 cm from the screen and the only thing you can think about is how good it's going to be to go to bed, you're not nearly tired enough.
Be efficient. Not only in the game you play or whatever it is you do, but especially in everything else. No more 30 minute showers, no more snooze on the alarm clock, no slow eating. Doing agility I had 2 * 7 seconds of slack every minute to do whatever I wanted, and I spent those 2 * 7 seconds to prepare most of my meals, and eat them as well. Don't slack on the hygiene, but be quick about it.
I don't know if this will help anyone, or if anyone even made it this far. I guess most people will never consider doing something like this. The text is based mostly on the experiences I got during 200m agiliy, where I did about 100 allnighters, a good handful of doublenighters and a few triplenighters as well. Right now it seems crazy to go more than 72 hours without sleep, but if you really want something, it comes much easier. As hard as it was depriving myself of sleep for as many months as it took, I loved doing it most of the way, and now 4 years later, I miss it from time to time.