Another point:

If both passengers have aisle seats, don't get upset if you ask the window passenger to switch and they say, "No."

I had this situation a year ago and politely said no. I prefer the window, so I don't have to wake up if my seatmate needs to use the restroom. It would have been better (and an even swap) for the person to ask the passenger in the aisle across from his/her companion. The FC newbie didn't figure that out until after we had taken off to ask the aisle seat.