DNS

Thats a big question!

This article from Microsoft will head you in the right direction as far as what to do from a technical viewpoint...

http://support.microsoft.com/default.aspx?scid=kb;EN-US;q237675

(Remove spaces from above link)

...but as far as specific configurations for your environment? Thats difficult without knowing what you want to achieve...

Cheers,
Tim.

Well, that's is not as simple as your question. It depends on what do you want to do.
I hope the next MS aricles can help you with it.
MS Q135919
MS Q164054
MS Q164213
MS Q163971
MS Q168322

Good luck,
@lberto