The latest issue of AugiWorld has a great article in it by Bruce Madsen about creating Families in Revit. It details the steps to go through, and provides some tips and tricks. If you are just starting to jump into creating families, it is well worth the reading!
Yuo can find AugiWorld online at www.augi.com, and if you are an Augi member, you can get a free copy of AugiWorld mailed to you every 2 months!