I'm creating a new theme for magento with twitter bootstrap.Can some one help me to do this with bacis step by step procedure.
Well I think I have just the right answer for you:
It's a really good explanation step by step.
You might be looking for ways to do this from scratch yourself but I would suggest checking out Webcomms attempt. They have worked with Bootstrap for Magento for a while but with the BS 3 release, they made their work public.
I didn't have time to implement it myself yet but from a quick look there are things like fully implementing BS navigation left to do but other than that it looks solid.