I do the Power90 workout with my wife six mornings a week before going to work, then I have a treadmill desk at work where I walk all day as I code, read, surf, post on /. If we have a really early or hectic day ahead we move the workout to before dinner. If we're sick or injured in some way we modify the workout a bit. The big secret is not to push hard, just show up and keep moving. The workout is for cardio and strength, the treadmill desk wiped out any aches and pains and bad posture from hunching over and typing for 20 odd years.
Give yourself three months of drill instructor attitude to get in the habit and aim at 3 years to measure your results, just to avoid any short-term thinking. That worked great for us, and now it's just natural to get up and do it.
That's pretty much all you need.