learn white hat hacking by following 4 steps

1. Study an operating system such as : Linux/Unix/Win NT, 2000
2. Learn at least one programming language(c/c++/perl/php/python)
3. Learn how networking technologies work(TCP/IP, Ethernet)
4. Join forums like http://hackforums.net/ to learn more
5. Take interest in CEH certification. Everything will fall along.

The below diagram is the heart of networking: