As good as strength training is for ramping up the metabolism, most folks are only in the gym 3–5 hours per week. That leaves a lot of time for sitting around, unless you do something about it.
If you have a desk job, take the stairs and park at the end of the parking lot. Get up from your desk and move around the office every 15 minutes. Go for walk breaks instead of coffee runs. Even stretching and fidgeting can help burn more calories and coax your metabolism along.