I'd second the sleeping socks and long johns. My socks are thick fleece; my long johns are synthetic blend with some merino wool. I've also found that, if my feet are cold, I can kind of wrap my down vest around them to fill the air space, and that seems to warm them up pretty quick. Likewise the hat, but I'm not quite as strict about that.

You do need to have the right hood - the best hoods I've found are, believe it or not, in Thermarest's down bags. I can sleep on my side without having an ear stick out (the Thermarest bags are bottomless; your pad provides the insulation under you; as a result, you can't roll the bag with you.)