http://www.scribd.com/doc/62823428/TNL- ... ng-Article
I came across this older article by Robert Sieveking in the National Locksmith magazine from 1990 and thought I'd share it. While dated, it's still good advice on the basics.
Incidentally, Robert Sieveking also wrote a book on the subject for National Locksmith Publishing. Although I've never seen it, I presume it's as professional and thorough as their other publications.