I always prefer to sit at the back. I always have checked baggage so there's no point in getting off the plane any earlier, just means a longer wait for the bags.

I'm always by myself so I try to get a window seat in the second-last or third-last row ideally where the aisle seat is already taken. The last unlucky few without seat assignments at check-in will be assigned seats starting at the front (wouldn't you rather have 14B rather than 27B given a choice?). If there is an empty seat on the plane I will frequently be the one sitting next to it.