Most infrequent travelers like to try and get a window seat, especially when they are flying into a new city so they can see the views. Those that have been traveling for a long time will know that its preferable to get an aisle seat. An aisle seat will allow you to stretch your legs more (just watch out for the food/beverage carts) and allows your better to access to your belonging that you may have stored in the overhead bin. After you land, it also allows you to deplane quicker.
A majority of airlines have restricted the forward rows of the economy class cabin and exit rows to preferred customers or those willing to buy up. If you are lucky enough to score one of those seats, usually you’ll get a couple inches of extra legroom. Most gate agents will randomly assign seats if the regular economy cabin is completely full and you don’t have a seat assignment. However, you will not be able to pick and choose your seat. If you go an check in online and the plane only has middle seats left, I would take a chance and check in at the airport. You may be in a middle seat, but at least you have a change of getting extra legroom.
Bulkhead/exit row seats may seem appealing for the extra legroom, but be warned. On most planes, the tray table is located in the armrest which reduces the width of the seat. If the flight is relatively empty and you want to stretch out, the bulkhead/exit row is not necessary the best seat to choose.
If you have to travel on one of the regional jets (Canadian Regional Jet/Embraer) I highly recommend that you pick an aisle seat. This is especially true if you are claustrophobic. The angle of the walls on these planes can reduce the amount of shoulder space that you have. Also, watch your head when you board the plane and get out of your seat. You won’t believe how many people I’ve seen bump their head since the ceiling is pretty low. On the planes that have a 1-2 configuration, most seats will have a small plastic button on the underside of the armrest, near the hinge. This generally works for all seats except for the exit row.
The last piece of advice I’ll give is for those flying on the Q400 Turboprop. If are located in the first class cabin, there avoid the exit row on the right side of the plane. For some reason, that position is one of the noisiest seats. If you have to sit there, bring a good set of ear plugs or noise canceling headphones.
To see what seats are good, I recommend heading over to SeatGuru. You can type in your flight number and view the seat layout with comments on what’s good and bad.