Within each class on an airline, some seats are better than others. So how do you pick the best seat on the plane ? First of all, ask yourself these crucial questions and than checkout the aircraft and cabin layout of your next flight

Window or aisle?
Both have advantages. If you like to stretch your legs during a flight, an aisle seat is good for you. Bear in mind, though, that this may be enforced upon you if the person in the window seat wants to get out of their seat. If you prefer to be undisturbed, then the window seat is probably best.

Day flight or night flight
On a night flight, window seats are preffered by many. You can sleep without being disturbed by anyone wanting access to the aisle, and in economy seats there’s the possibility of resting a pillow or rolled up item of clothing against the side of the aircraft to prevent head lolling.

In general:

Middle seats are to be avoided.
So in a 3-4-3 configuration, typically designated A, B, C, then D, E, F, G and then H, J, K (I is omitted to avoid confusion), the set to avoid are B, E, F and J.

Avoid seats at the back of the plane.
In general, the front of the plane is the quietest, because in front of the engines (though for a few seconds hen the front landing gear is lowered or raised). The middle of the plane noisy because of the engines, but is smoother. The back of the plane is both noisy and bumpy.

Avoid seats next to toilets
Unless you are a heavy drinker or have a medical condition, these seats are noisier, often have people queuing to use them (and so standing over you) and can often be smelly as well.

Avoid seats close to the galley
For a day flight being here may be an advantage, since you can receive service more easily, or in premium cabins, perhaps serve yourself. But on night flights the noise can be a nuisance from cabin crew talking to clearing up and there is always a lights shinning out of the galley.

Seats by emergency exits are to be preferred
These give more leg room, though they do come with restrictions, most notably that you are able bodied and so can assist in case of emergencies, and of course you cannot stow your luggage under the seat in front of you. Bear in mind also that these are often close to the galley, and so can be noisy.

Bulkhead seats
The bulkhead is a dividing wall between cabins. If you have a seat facing this, then you will probably get more legroom, but also bear in mind this is where babies are often found in bassinets. And no amount of leg room compensates for a noisy baby on a night flight. Also make sure not to sit in the room in front of the bulkhead, since the recline of your seat may be fixed or restricted.