To make sure I add plenty of movement to my day, I set an alarm on my cell phone to go off every hour. At that time (it doesn't have to be "on the hour," just once every 60 minutes), I get up from my desk and move around for 5-10 minutes. I work at home, so I use this time to perform housework (vigorously), strip and re-make the beds, take the dog outside and throw the ball while jogging in place, or otherwise physically move my body. The cell phone reminder really helps!
If you work in an office, you could use your hourly break to climb the stairs or step outside and walk around the building. It's surprising how far you can walk in just 5-10 minutes!