It's easy to reach 10,000 steps at work when you go to the next furthest water cooler for refills, go to the far restroom. Try walking to your co-workers instead of e-mailing. I work in an auto plant and found that I can reach 1/3 of my goal in the first two hours of the day just by "going long".
Get a pedometer for starters. If you're just starting out get a simple one.