You've got to be active every day. It's got to be fun, or if you're like most people, you won't do it every day!
The way to be physically active is to think of exercise as playing. Instead of doing something you consider drudgery, or forcing yourself through a painful, boring routine, or joining an expensive health club - go to a park and play. Swing on swings, climb a tree (if you can!), run around a merry-go-round and have a good time. Bring a ball, and see if you can make some baskets, or toss it into the air or back-and-forth with a friend.
Play for a half hour a day at least, and you'll see how much fun it is. Instead of exercising.