You're already: Sitting while listening to music or talking on the phone (25 calories for 20 minutes).
You should also: Practice the piano. This childhood hobby that you're always pledging to pick back up can help you burn 95 calories in 30 minutes.
Bonus tip: Buy sheet music of contemporary songs you love so you can play backup to Adele and Rufus Wainwright. The more you throw yourself into "Someone Like You," the better.
Calorie counts are based on a 160-pound woman, using data from The Compendium of Physical Activities Tracking Guide from the Prevention Research Center at University of South Carolina’s School of Public Health.