I do things I like to do - like walking with an mp3 player. I walk 4 km every day (or 3 miles). It may not seem like much but it ends up being 20 km or 15 miles every week
I have to take two busses to work... one bus is about 20 km, the other is 2. I walk the 2nd bus route to and from work when weather allows it, and i feel so much better for it. In fact I get a walking buddy from my office once in a while as she is starting to pick up on the habit. My problem is she tends to walk slower lol.
Also, playing with kids - kick a soccer ball around, play some basketball, join a softball team, go golfing - lots of fun things to do and it won't even seem like youre exercising, just having fun.
Do you like to swim? How about water slides? Sledding? Skiing? It's all exercise and all very fun