You can start by searching around the internet. There is tons of tutorials on the subject.
Also, if you're into looking at source code, I know a guy that developed an instant messaging program specifically designed for security and cryptology. It's supposed to be the safest way to talk over the internet.
It's all opensource (written in Java) so you could take a look at that.
http://www.seclude.org/
And if you e-mail him about cryptography, I'm more than positive he'll be more than happy to talk with you about it, he loves the subject. His name is Martin (you could also talk to Kris). Anyways, hope this helps some.