There is a whole array of tactics used in bike racing. Because I am unfamiliar with much of the team tactics at play in racing you can look here to learn some more about it.

I will however shed some light on an important facet of racing tactics, drafting. Drafting is a technique where one rider pedals them self very close behind another rider. As seen in the picture on the right, the rider in back has much less wind directly opposing his motion. This can save the drafting rider up to 40% of the energy it would normally take to ride alone (Start bike racing).

During a race speeds are very high. When velocities are increased so is the force of the wind countering the riders movement forward.  Thus is high speed sports such as bike racing drafting is a vital strategy for any competitive racer. The more work done by a competitor the better, especially when you your self are reaping the rewards of their hard effort.