From the minecraft thread...
For us it's been an ongoing challenge. For the most part we do pretty well, but if we stop trying we discover ourselves sliding back into overly sedentary habits. We're a family of geeky introverts with petite bodies, contending with long winters and (worse) long cold wet shoulder seasons. In some ways we have it easy: we live in a wilderness setting. But that has its challenges too: we're so rural that there are no local organized sports, no community recreation centre, no arena, no swimming pool, etc. So, yeah, it can be a challenge.
We talk regularly about whether we're maintaining a healthy balance and we do have to keep at it.
Organized physical activities have helped, even when we have to drive a long way for them: in the past we've done aikido, gymnastics, swim lessons, community soccer, downhill skiing, XC ski club, skating lessons. Putting my kids in touch with other people who are involved in enjoyable regular physical pursuits is worth a lot in terms of internalizing that as "normal."
We have a bunch of accessible home exercise equipment: yoga mats, a chin-up bar, gym rings hanging from the ceiling, a (new last month!) a treadmill in the basement. We've spent money on decent quality mountain bikes and XC skis, and have equipped the outdoors with interesting options: ramps, beams, ropes, treehouse, bars, sometimes an outdoor skating rink.
And then we do what we can to model and directly encourage physical activity. We garden, we have a dog, we've raised chickens, we suggest going hiking, camping, canoeing. I encourage the kids to volunteer with me to help out at outdoor events like the ultra endurance race we staffed aid stations at a couple of weeks ago. I run several times a week. I mountain-bike and road-bike regularly. I downhill and XC ski through the winter. Now that the kids are old enough I go out an exercise even when I can't talk them into coming with me ... and I don't worry about it, because I can see that they're internalizing the message that it's important and normal for grown-ups to stay active. I'm not a fan of biking simply because it's good for them. It's important to me.
I grew up with parents who didn't put much stock in exercise. It took me until adulthood to begin to find pleasure in pushing myself to higher levels of physical fitness, to get involved in sports, to start really being active. I had a long period of insecurity and self-consciousness that I had to work through first. I want my kids to grow up with a different experience: having confidence and comfort in exercise and physical fitness. So I do stack the deck a fair bit in favour of that stuff.
So far my kids do seem to be picking up some pride and confidence in their fitness habits and abilities. It is an issue that requires constant attention, but by age 10 or 12 or 14 they seem to have internalized that nudging for themselves. Dd19 is living on her own and runs three times a week and works out at the gym regularly. When she was home this past summer, she wanted to spend her days off doing monster hikes into the alpine. Ds17 is wiry little guy who is a chin-up powerhouse and lifts weights a bit for the heck of it. Dd14 is on a volleyball team and her favourite "date" with her boyfriend is a 5k trail run they do regularly. From 8 to 12 or so seemed like the toughest ages to keep them physically busy, but the values seem to have soaked through eventually.