Consider flying aircraft that have the fewest middle seats
I love 767s because there's only one middle seat per row. This means that your chances of getting one are less than on any other two-aisle aircraft: A 767 can be 86 percent full before anyone gets stuck in the middle. Two-aisle planes tend to give you bigger seats, more legroom, and larger overhead bins than one-aisle aircraft. Within the United States, try to travel on planes configured for international flights. These often fly from an airline's hub to an international gateway before continuing overseas (e.g., certain American Airlines flights between Dallas and San Francisco).

Compare seat dimensions
On domestic flights, coach seats vary in width from 16.5 to 18 inches and in pitch (the distance between two rows of seats) from 30 to 36 inches. Internationally, they usually range from 17 to 20 inches in width and from 31 to 42 inches in pitch. The seat you'll find most comfortable depends in part on your body type. Say you're choosing between one aircraft whose seats are 17 inches wide with 32 inches of pitch and another whose seats are 18 inches wide with 31 inches of pitch. The tall and skinny will prefer the former, the short and hefty the latter. Charts on SeatGuru let you compare seat dimensions on a slew of carriers. Remember that you can pay a few extra dollars for more legroom on JetBlue and United.

Compare entertainment options
It's no surprise that Condé Nast Traveler readers voted Virgin America their favorite domestic airline last year: Its coach seats are 19.8 inches wide with 32 inches of pitch and have personal TVs with AVOD, as well as AC power ports. The good news is that more carriers are putting AVOD in coach. Delta has installed it on some 757s, and Continental is adding it—as well as a choice of up to 250 movies#151;on its 777s. JetBlue has 36 channels of live TV.

Always select a seat at booking, then keep checking for better options
When you're buying a plane ticket online and you click to the aircraft's seat map to assign yourself a seat, compare it with the corresponding seat maps on both Seat­Guru and SeatExpert. No good seats left? By all means assign yourself a seat anyway: You never want to arrive at an airport without a seat assignment, and you can likely change it later. If for some reason online seat selection is not available, phone the carrier and try to get a seat assignment through the reservations agent. Return to the airline's site several times before your flight date to check whether a better seat has opened up. When you check in online, do it as early as possible; you'll often see that seats have become available that weren't before.

Try for a seat in the emergency exit row or right behind it
Although exit-row seats sometimes don't recline, they typically provide extra legroom and often are not assigned until the day of the flight. Sometimes you can pay extra to get one, sometimes you can get one for free by asking at the airport. None available? If you know that a plane's exit-row seats don't recline, ask if a seat is available in the row behind the exit row: There won't be anyone reclining into your lap.

Ask the gate agent to move you
Unless I've achieved my personal nirvana of an aisle seat in an exit row, I always ask the gate agent if a better seat is available. Preferred seats (e.g., aisle seats up front) often open up at the gate because the elite-level or full-fare passengers who were occupying them get upgraded at the last minute.

Become a member of an airline lounge club
Club agents, in my experience, have magic fingers when it comes to using the computer keyboard to get you a better seat. At various times I've belonged to the American, Continental, and Delta lounges, and, as a consequence of friendly conversations with their front-desk agents, have ended up with everything from a row of seats blocked off next to me (so I could lie down and sleep) to a free upgrade to business class on Christmas Eve.