If you are in an exit row, get on early. Especially applies to the Embraers, where if you are in rows 1 or 2, you are fighting for space with oxygen equipment, spare High Lifes and crew bags. And for row 12 there is pressure for space as you can't put anything on the floor in front AND you need to get on before the Tumi-clutching masses who can't bear to be parted from their bags.