I don't have status on any airline/alliance, so when it comes time to pick seats my choices are usually pretty limited.

That being said, I usually try to pick a window in the back 1/3 or 1/4 of the plane, unless I know I have a tight connection.

Reasoning -

1) Window = View. Love the view from 35K feet.

2) Back = Earlier boarding, which means I might get some overhead bin space before they're all gone.