Cadence is the key

A summary quoted from the original article at Spin Cycle - Bicycle Victoria

Maintaining a high cadence is part of good cycling technique. A few of the basics to remember are:

• Try to maintain a constant cadence. A cadence of 90–100 is best for riding on the flat
• Learn to use your gears. Small or low gears refer to gears that are easier to ride in (small ring at the front and large ring at the back). Big or high gears are the reverse (big at the front and small at the rear) and are harder to push
• Be aware of when you are starting to slow down or speed up and change gears accordingly
• Smooth gear changes decrease the chance of your losing speed
• Avoid 'grinding' away in high gears as this generates muscular fatigue in your legs and can cause you to lose efficiency
• Change down a gear coming into corners or at the start of hills and try to keep your cadence up.