I would really suggest purchasing a good book about it. From my point of view, I would go for "Hacking: The Art of Exploitation, 2nd Edition" from Jon Erickson which goes in depth about how to crack programs using gdb and other tools. It's really a wonderful book if you want to learn more about the world of cracking in general, and it doesn't require much prior security experience.

Quick link to Amazon: http://www.amazon.com/Hacking-The-Art-Exploitation-Edition/d...