answer:Where are you riding? Road, rail trail, off road, mountain, etc? What kind of bike? Road, Hybrid, mountain? Wear a helmet if you are in traffic, mountain, going anything over 15 miles per hour, or if you are a novice. What do you want to accomplish? Is this casual enjoyment, trying to get fit?, training for a century? All of these matter depending on what your goals are? In general, you want ride at an aerobic level and at as high a cadence (pedal revolutions/min) as you can maintain consistently over the whole terrain if you are doing anything serious. If it is casual, it does not matter.