Depending on your carrier, your plane will most likely be organized into a first and economy class. Air carriers have authority over how these seats are configured (so if you’re going to blame someone for your lack of leg room, give Airbus and Boeing a break) and often there will be multiple configurations per model.
For example, the 737-300 (or 733) bulkhead starts in row 5 and is generally a coveted seat, but the 739’s bulkhead starts in row 7 and is right behind the lav, making it less desirable. There are similar iterations for other jets; the A330 is often listed as the A332 or A333 depending on how large the business and first classes are. You get the picture.
Airlines also control who can sit in where in their section of the plane. They like to reward frequent and elite travelers with special seating privileges, so sometimes they’ll block off exit rows, bulkheads and aisles near the front of the cabin. As a result, not only are regular coach passengers limited to economy class, they may not be able to sit in the better parts of economy class.
Your job is to find the combination of good seats, available seats (that nobody is sitting in) and permissible seats (that the airline will let you sit in) then jump on it before anyone else does. This can done with a quick balance of seat map and availability checking at your carrier’s website.
Continue on to web tools and seat selection.