Cyclelicio.us puts together a really good and useful set of tips and tricks to get the most compelling and pleasing photographs of cyclists.
Summarized here (and expanded upon there), they are:
Get close to the action.
Focus on the face.
Depth of field.
Avoid downhills and straightaways.
Know your autofocus and sensor lag.
Freeze the action.
Finally, STAY OUT OF THE WAY!
Very good stuff indeed!