Given what happened with the wedding of 'lex Pendragon and Marlise this past weekend with some of the attendees and celebrants having problems attending due to delayed airplane flights or layovers due to weather, I think it'd be a good idea to post something about camping out in airports: Why you might have to do, how to do it, and what to look for.
While there are some people who actually plan to camp out in airline terminals for various reasons, most people don't. Those of us that do are usually constrained by transportation to the airport to begin with: Daily rates for parking cars in the lots are exorbitant, and you can't always find someone that can drive you to the airport at 0300 so you can catch an 0600 flight. Or, during this time of year, you can't always find someone who can drive you to the airport at 0300 so that you can catch an 0800 flight because the security checkpoints are backed up to the tune of hours in line (which I encountered, incidentally, during my trip to Palo Alto, California). Under such circumstances, it makes sense to arrive at a time reasonable for your transportation (say, 2200 local time), navigate security, and then find someplace to camp out for the night.
Another reason is that flights may be delayed or canceled out from under you, and you'll have to wait some period of time before another flight becomes available. If you're lucky another flight might be two hours off. If you're not it might be seven hours off, or the airline could advise you to stay in a hotel for the night. None of these are particularly pleasant affairs, but if you're stuck in a strange city waiting to catch a plane you do what you have to do.
Edit: Google now has a feature in which you can query your airline and flight number, and it'll tell you the status of your flight. First off, travel light. Take it from me, it sucks to haul around a thirty pound field kit, a coat, and a suitcoat (or something appropriate). If you can get away with it, carry no more than thirty pounds of stuff in total. Bear in mind, however, that a coat can be used as a blanket if you need to curl up for a couple of hours. I bring my leather trenchcoat during the winter for just this reason. I'd also recommend catnapping when you can afford it, working on your self-hypnosis or meditation techniques if you can't (I do this while I'm on the road, and refer to it as 'elf napping').
Sleep as close to your gate as you can to minimize disorientation, and so that another traveler will (hopefully) wake you up in case you oversleep. If you can, stretch out on the floor next to the wall to save your back; chairs and benches will do in a pinch but you'll probably wake up sore in the morning. Bring an alarm clock or set your phone/PDA/mp3 player/laptop to wake you up a half hour before your flight is supposed to board so you can clear the cobwebs out. I often sleep while using my carry-on luggage as a pillow just in case anyone gets any funny ideas. In fact, always carry your stuff with you, because airport security is supposed to check any unattended baggage for explosives or suchlike. Don't sleep near any restricted areas, because security guards will give you a hassle.
Secondly, make use of whatever power outlets that you can get away with using. Keep the power cells in your phone and PDA topped up in case you need to talk for extended periods of time to set up another flight or get crash space with someone. Keep your laptop charged up, too. These days, most everything essential to travelers involves electricity in some form.
Third, don't listen to your iPod too much. As I discovered the last time out, you can miss an announcement (like a delay retraction followed by a gate change) if you're not paying attention.
Fourth, something to do if you can't sleep. Bookstores at airports close at weird times, and it's possible to find yourself bored silly without something to read. I tend to bring two or three books with me on long flights (with another six or seven in my suitcase to switch out after I arrive) and a DVD-ROM disk full of e-books. If you like to code, bring some projects to work on; I guarantee that you'll make progress. I do some of my best hacking while waiting for my plane, if not while actually in transit.
Fifth, communications. There are still airports out there that don't offer free wireless to travelers. Services like T-Mobile are often available but personally I don't trust sending my credit card information over strange wireless networks. If you can, purchase one of the pre-paid debit cards that are popping up all over the place and use it to pay for net.access - Visa and AmEx cards are available in supermarkets for decent prices these days, so buying one or two isn't a bad idea. If you can purchase T-Mobile Hotspot pre-paid cards... please tell me where I can find them in northern Virginia, because I could really use one right about now. If you have access to a cellular network card of some kind, I suggest making use of them while you're stuck.
Sixth, food. Not all places in an airport will be open at 0-dark-thirty, so have something handy to eat. I tend to pack a couple of Clif Bars in my field kit for cases of the late night munchies. If you'll be in for the long haul, try to eat a real meal before the restaurants close, even if it means hiking halfway across the terminal. You won't be sorry.
Seventh, facilities. Before sacking out, walk around a bit and make sure that you know where the bathrooms are. The reasons for this should be obvious, especially when it's cold in the terminal.