Claas Kuhnen put online a serie of 21 videos explaining the basics of Cycles rendering.
If you’re confused about scene and node setup, this very progressive introduction should give you a good start.
It’s clear and didactic and you have some useful tricks also.
Another great video by Jonathan Williamson from Blender Cookie about the bases of texturing with Cycles.
You will see how to add a diffuse texture and how to improve the result with bump mapping and specularity.
Jonathan Williamson explains how to create a blend file used as a node library for materials or compositing functions.
You must create nodes groups, give them a proper name and save all this in a blend file. After you can link this file in your work file or even better, link the file to the default startup file by saving you user preferences just after creating the link.