Simply asking how to overclock is almost like asking us how you should live your life. Its too broad of a question to awnser without practicly writing a book.
If you look at the stickies in a few sections of this forum it talks about overclocking, I would sudgest you start there.
Go research it on the net, rather then us trying to explain whats already been explained, there are literly millions of topics about overclocking.