When crossing the pond westbound I always sit on the right hand side to avoid the sun and the same with westbound US transcons. Reverse this for eastbound flights. I sometimes deviate from this though if I know the destination airport has a spectacular approach best viewed from the other side.

On a similar theme I always sit on the left hand side for overnight transatlantic eastbound flights (particularly in winter) in the hope of catching a glimpse of the Northern Lights which I often have. I'm not the kind of person that takes kindly to the request to lower window shades