Used to be only window. Now I shoot for the following:

1. Business/First: Always window
2. Short flight (2 1/2 hours or less): Window
3. Longer flight on a narrow body A/C: Aisle
4. Transatlantic coach: Aisle
5. Widebody - Depends on seating config. If it is 2-4-2, I'll take a window. Otherwise, aisle.
6. Have to try to clear customs and make short connection: Aisle