You already: Hop on the elliptical trainer (134 calories for 30 minutes at a moderate pace).
You should also: Use the moving handles to pump your arms, which is said to help increase the burn by up to 30 percent (174 calories for 30 minutes at a moderate pace).
Bonus tip: Bob likes to have clients do a mix of arm and ab intervals. Every few minutes, they'll grasp the central stationary handles, tighten their abs, and focus on stabilizing their core as they move their legs. He says this probably burns about the same amount of calories as using the moving handles—and it's a killer way to tone the abs. (Do enough intervals to fill 40 minutes in order to shave off 100 extra calories).