Also, a lower gear/higher spin ratio is a better combo for a better workout. Running a higher gear ratio requires more strength, which is akin to lifting weights, good for building muscle, but not for burning calories.

A lower gear ratio will make you spin more, along the Ken's aforementioned very good advice. This lower impact method will make you burn more calories, get into shape faster, and help your muscles gain that "muscle memory" that help improve your technique.

I started out around 70ish and now am running 48/17, which works well for me here in hilly San Francisco.