Not all coach class seats are created equal. In order to get the best seat possible, you should check out the websites SeatGuru and SeatExpert when selecting your seat, as these websites have comprehensive reviews of the seats on most airplanes for most airlines. You may want to check these before you actually book your ticket, as you may have the choice of flying on different types of planes, some of which may have better legroom or newer seats. Note: This is not foolproof. Sometimes, airlines switch the equipment you are flying on due to maintenance or loads.
If you are booked in coach, your best seats will normally be the bulkheads and the exit row seats. However, a few notes about bulkheads, which are probably the most controversial seats on planes:
- On long haul flights, people traveling with babies are more likely to be sat at the bulkhead,
- Bulkhead seating may be reserved for the infirm or handicapped,
- Sitting at a bulkhead may mean sitting right next to a bathroom,
- If near a bathroom or galley, there will be much foot traffic near your seat during the flight,
- Occasionally, bulkheads actually have slightly restrictive legroom, and
- In almost all cases, bulkhead seats are slightly narrower, as the tray table will be in the armrest.
However, what is excellent about bulkheads is that there will never be anyone reclining into your space. Exit row seating also varies, but much less. Exit rows generally give you between 3 and infinity inches of extra legroom, but seating in them is restricted to people who meet the lenient requirements. Beware however, that on some planes the exit row doesn't give you any more legroom, and in some exit rows, there may be reduced or eliminated recline. Occasionally, on widebody planes, the legroom in some exit rows may be affected by the slide, which extends out of the door.Reserving these special seats (bulkheads and exit rows) has recently became (on most airlines) a luxury reserved to the people who are elite members of the airline's frequent flyer program. Note: In the case that you fly frequently, you may desire to fly on only one airline, as this will give you the best chance to make elite in their frequent flyer program, but that's a topic for another node. However, should you not be an elite, do not become depressed. As soon as the check-in opens, the seats are released for choosing by anyone. This is a reason that you should check-in as soon as you can. With the advent of online check-in one can check-in early from the comfort of their own home.
On some airlines, you can also buy up to premium economy, which generally has enhanced legroom/recline, and sometimes has other special features such as fancier cuisine, priority boarding, built-in massage, and improved in-flight entertainment. While this does cost additional money, it is not as expensive as business, and can be a godsend if you are flying from Chicago to Tokyo.
An alternative way to do things, if you have flexible travel plans and you are on an oversold flight, is to offer your seat to the gate agent. This is called Voluntarily Denied Boarding, or VDB for short. If you are nice to the gate agent, and there is room on the next flight, you may possibly be able to ask for and receive an upgrade to business class on your next flight. However, do not just assume that will happen if you give up your seat. Be assertive. They aren't required to do that, but it is worth a shot. This might not literally be getting a first class seat in economy, but it'd be paying for an economy ticket and getting a business class seat, which I'd find to be better. | 
