One way to passively burn more energy that I don't see mentioned enough is to simply lower the ambient temperature (and don't add more clothing). Staying in a cooler room (or not using a heavy blanket when sleeping, etc) can use a significant amount of extra energy. Sleeping humans use between 20 and 80 kCal/hour, depending on ambient temperature, blankets, etc. (80-20)*8=480kCal potential burn, per night of sleep. Over the course of a week that's 3360kCal, or nearly a pound of body fat's worth of energy. Use your basal metabolic rate to burn more energy by staying in cooler environments.