Anybody who travels much, and non-rev'ers in particular, will eventually find themselves stranded at an airport late at night, with many hours before their flight the next morning. Most people, when faced with this situation, will try to find a cheap hotel near the airport. If you're a businessman on an expense account, traveling with family, or able to split the cost with a friend, this is probably your best option. If, however, you are a broke regional airline first officer who is traveling because 1) it's free and 2) free onboard meals, there is only one option: sleeping in the terminal.
Over the years I've slept in airports a number of times. Most recent was this Thursday night. I was in Seattle for a screening and release party for BT's new album/DVD, This Binary Universe (it's very good, btw - highly recommended). After the club closed at 2am, some guys I met dropped me off at the airport, where I slept until my 7am flight to Portland. This got me thinking about past experiences, and I realized that sleeping well in airports requires some specialized knowledge...which I am more than happy to pass onto you, the Broke Regional First Officer.
Two enemies of sleep are ever abundant in airport terminals: light and sound. Many airports are rather brightly lit so as to avoid burned out road warriors becoming depressed and killing themselves (that's my theory, at least). A few energy-savvy airports turn the lights down low at night, but many do not. Another ubiquitous feature of modern airports is the presense of loudspeakers that regularly blast security announcements. I think sleeping in airports would be a very efficient way to train TSA agents; they would learn the list of prohibited items by osmosis. If you're sleeping near an entrance, you'll also become intimately aquainted with what exactly the white and red zones are for. Unless you're a heavy sleeper, I would suggest packing a sleep mask and earplugs on any trip where you may end up sleeping in an airport.
Airport terminals tend to be on the chilly side, so bedding is a good thing to have. I think you'd have to be pretty pessemistic to tote a sleeping bag along on every trip! However, on your inbound flight you'll probably have a good idea whether you might spend the night in the terminal, and you can grab an onboard pillow and a blanket or two. That's assuming you're not traveling on an airline that has eliminated them as a cost saving measure. In a pinch, a jacket or extra clothing can help keep you warm in a icy terminal.
When looking for a spot to sleep, inside security is preferable. It's usually easier to find areas without excessive light or sound around the gates, there are typically more seats to use, and you and your belongings are safer there. Unfortunately many airports close the gate areas after 1 or 2AM. If you can make yourself inconspicuous, you may avoid eviction. Bedding down behind gate counters works well for escaping notice, although I'd suggest you move on before the gate agents arrive for work in the morning. If you're approached by a security guard, pretend to be fast asleep. Snore, mumble as though dreaming, and maybe even drool a bit. There's a good chance they'll leave you alone!
If you don't wish to sleep on the floor, you may be able to find a bench or row of chairs without armrests. These can be hard to find and often get taken early in the night. Back in the "good ole days," seasoned airport sleepers would carry a screwdriver along to take armrests off of chairs! Of course, all such tools are strictly verboten these days. However, you may be able to move around the furniture a bit to form a passable bed. A few airports have started providing cots and even some bedding to stranded travelers. This is more common during massive disruptions such as snowstorms, strikes, terrorism-related groundings, etc.
When you sleep in an airport, you accept that you may not catch much actual sleep. I've found that it's easier to keep myself awake for a while by reading, blogging, playing cards, etc, until I'm really getting tired, and then I'll lay down and get two or three hours of good, uninterrupted sleep. In the morning I'm more rested than if I fitfully tried to sleep all night long. I just plan on catching additional sleep on my next flight.
You'll sleep better if you're sure that you'll wake up before your flight. Unless you're a heavy sleeper, all the activity in the terminal after 5am will wake you up. A travel alarm clock or wristwatch alarm can provide extra peace of mind, though.
Keeping your belongings safe is always a consideration, particularly if you're sleeping outside of security. I'll often use my backpack as a pillow. If I don't have a blanket, I'll take my wallet out of my back pocket & sleep on it. Sleeping with your bags under your bench or between you and a wall should discourage would-be thieves. Those traveling alone, particularly women, will be safer sleeping near other travelers.
If you have a military ID card, many airports have USO lounges with couches or even bunk beds as well as complimentary snacks and beverages. If I had this option I'd never pay money for a hotel room again!
The most experienced airport sleepers have their favorite nooks and crannies at the various major airports. You can read many of their tips at www.sleepinginairports.net.
One last tip. If you're stuck in the western US and you can jumpseat, consider taking a redeye rather than sleeping in an airport. For example, if you're trying to get to Nashville and you get to Denver after all the BNA flights have left, you might be better off taking a redeye flight to New York or DC and then catching a flight back to BNA. Depending on the flight loads, you might get better sleep than if you slept in the terminal, and you'd probably get to BNA at about the same time as if you'd taken the first flight out of DEN. Plus you might get free breakfast on the morning flight!