Coach flight, sold-out: left-side aisle.
Coach flight, lightly loaded: wherever I think there will be an empty middle, but aisle if possible.

Premium cabin: always window. If it's a J configuration that spans a couple subcabins, then I want to be in the smaller subcabin. Upstairs on the UA 744, left side on the AC 767, always Row 8 on the old UA 777 configuration, in the nose of the 744 for airlines who have J downstairs (LH). But no matter what, I want window in J/F.

If I was looking at a truly empty cabin with everything else being equal, I might try to anticipate the view at departure and/or approach. But in reality this usually isn't an issue because at least some of my desired seats are already taken...