Get down at a block before your destination and walk the rest of the way. You might not have time to fit in long walks in your busy schedule so this is one way of ensuring that you at least get to walk for a little bit every day. If you take the bus or the subway, get down at an earlier station and see if you can walk the rest of the way.
If you drive to work, see if you can get space in a parking lot that is a little away from your office.