The Revit Imperial or Metric Tutorial PDF file has a fairly extensive section (approx. 200 pages) on creating content - Families. YOu can download a copy of the entire tutorial PDF file from Autodesk website under Revit Documentation. This will get you started. Also, there are a number of tutorials on AUGI, AECBytes, Blogs, etc. and many other sites hosting Revit information.
Mel Persin, AIA
AEC Technology Consultant
Technology to Visualize and Realize Solutions
MasterGraphics, Inc.