I'm lucky enough to work within 5 minutes of a gym. So, instead of going out to lunch or just killing time, I head over and get a good 30-45 workout it 4 or 5 days a week. I eat my lunch when I get back to my desk.
Whether you workout in a gym or at home, you should create a plan of daily workouts. Start with one week at a time and write down what you're going to do on each day and for how long. If you get extra exercise in, it's a bonus! Also, try to alternate between exercises to avoid getting bored.