Flight Plan

Whether you are coming in on a 23-god-please-let-it-stop-hour flight from Sydney Australia or just a 9 hour from London's Heathrow to New York's JFK, there's no reason you shouldn't aim for the best seat on the plane.
Apart from praying for a safe flight, I also pray that the person next to me has a sense of personal hygiene and space that is relatively similar to mine.Of course depending on what sort of aircraft you fly, there will be variations in the seating plan but there are still ways to maximiise your comfort during flight.
LAST THREE ROWS: If you are auto allocated these seats keep them! I remember the first time that I saw 'Row 68' on my boarding pass and I almost fainted, but it's actually one of the most spacious seats available with overhead cabin storage and extra room down the side due to the fact that there are only two seats and the curve of the plane.
Also (after first class, business class, children and people that need extra boarding time) you are the first to get on the plane which is a surprisingly welcome change from waiting around the terminal especially if you have already been there for the couple of advised hours leeway.

EXIT ROW: Three words - extra leg room.
This is obviously always a safe bet and if you aren't begging for it at check-in you should be (I have a 'friend' who turns up extra early so she's guaranteed this seat). However, you will be given the responsibility of prying open that tightly air sucked emergency exit door if some horrific accident should occur, although I doubt anyone would blame you if you didn't considering how comfy and asleep you would be in that spacious exit row position.