If you've ever traveled on a commercial jet, you probably know to avoid picking the middle seat in a row of three. If you purchase a last-minute ticket or you didn't select a seat before check-in, you might not have any other choice but to sit between two strangers on a long transcontinental flight, but assuming you do have your pick of where to sit, it's worth spending a few minutes to make sure you're getting the most bang for your buck.

An air carrier's seat map may highlight certain rows as having additional legroom or a missing seat in front, but airlines typically leave out a few critical details that can mean the difference between a decent flight and a miserable one. Take the row just behind a bathroom for example, or one adjacent to the galley, where chatty flight attendants tend to gather between beverage services on a redeye. You don't want to end up in either, but without some input from passengers who have traveled on the same aircraft type in the past, it can be tricky to know which seat to pick.

Sites like SeatExpert and TripAdvisor's SeatGuru take the guesswork out of selecting an ideal seat. Both sites display similar results, but it's worth dropping by both SeatExpert and SeatGuru before you pick a seat for any upcoming flight. SeatExpert lets you locate the aircraft type using your airline name, flight number, and date of departure, making the process a bit more straightforward for novice seat pickers. If you're already familiar with your carrier's fleet (you know a Boeing 737-900 from a 737-800, for example) SeatGuru is probably your best bet.

To get started with SeatExpert, enter your flight details and click "Find your Seat." If all goes well, a detailed aircraft layout will pop up, with seats colored green (a good seat), yellow (less than ideal), orange (worth avoiding), and red (avoid at all costs). White seats are average, and if you end up there, you should be just fine. Naturally, you'll have the best experience in a green seat, which typically offer more privacy or additional legroom. Red seats, at the other end of the spectrum, are often located near galleys or lavatories, and may lack a window, floor storage, and a normal amount of legroom.

SeatGuru includes additional info, such as a list of in-flight amenities and reviews from people who have traveled on that aircraft type, along with green, yellow, and red color-coding for great, poor, and terrible seats. You'll find a bit more detail with select seats as well -- for example, the seat map for United's 787-800 (Dreamliner) makes it clear that seat 27L has restricted legroom, a tiny window, and a tray table in the armrest, giving you less space to sit. 16L, meanwhile, has heaps of extra legroom thanks to its bulkhead position behind the business-class cabin, though you won't have space to store belongings below the seat in front.

Airlines have caught on to the demand for better seats, of course, labeling preferred rows as "Economy Plus" or "Main Cabin Extra" and charging a premium for a more spacious seat. Oftentimes these roomier rows are located in the front near the restrooms and baby basinet locations, however, so even though an airline may charge the same premium for two seats with comparable legroom, you may still have a better (or worse) experience in one location than another. Just as you might not get a better return when you blindly purchase a higher fare or a more expensive bottle of wine, the same applies to pricier seats.