If you're in the North American area I would recommend books like this one to get started and learn about the many different aspects of locksmithing,
http://www.amazon.com/Complete-Book-Loc ... 635&sr=1-1
If Bill Phillips books start to bore you, you can venture into Marc Tobais's book "Locks, Safes and Security". You can get a copy here,
http://www.ccthomas.com/details.cfm?P_I ... 0398070793
Then there are a couple good correspondence locksmith courses you can take to get you a more structured hands on exposure to basic locksmith work and allow you access to a lot of special locksmith tools you may otherwise have a hard time getting. Foley-Belsaw and Assured Locksmith Training were the two I've taken and I think they were worth the money.
But ultimately try to search around this site as much as possible because there are a lot of locksmiths and other very knowledgeable people here on this site who have posted very useful and insightful hints and tips regarding locksmith work. Lots of helpful people on this site.