Airlines these days are making us pay dearly for little pleasures like choosing our seats. It's our job, therefore, to have as much information as possible when doing that. We all know if we prefer window or aisle, but choosing a seat goes way beyond that.
For example, if you prefer a window seat for a great view of the Statue of Liberty as you fly over, you want to be sure that view isn't blocked by the wing of the plane. Or if you like an aisle seat, you want to be sure you're not too near the toilets and have people hovering over you the entire flight.
Other factors to consider vary from aircraft to aircraft. Will your flight have entertainment stations in the back of each seat, or will you be forced to crane your neck to see the screen above the aisle? Which seats have the best view of those screens?
It's also worth knowing which rows are exit rows and which are bulkhead for maximum legroom, although you may end up paying for that as well.
That's why I always check my flight on Seat Guru before I book. The site has diagrams of every aircraft, with the seats colour-coded to help you choose. You can even search for your flight and it will tell you which aircraft you'll be in.