Keep moving. Don't sit around.
The most important things is to be active. Like, always moving, always doing something. Never sit, unless forced. I've very active, but I'm one of those guys who can order a pizza, eat the whole thing, and really not notice.
Excercise is ok, but people tend to do it, then sit around the rest of the day, which kinda ruins it. Find a sport, get active, stay active, and you'll lose the pounds without noticing.