I have an an forum which is not that active, i am looking to close it & Redirect it to One of my active forums.
Which redirect should i use 301 or 302 or none of them ? 
You can simply do:
Redirect 301 / http://www.domain.com/
^^Ok, Thanks. But i will sell this domain later, Any problem in that ??
No, because the buyer will setup their own nameserver configuration, so their hosting will be linked to that domain.
Thanks again.
Out of curiosity, what's the difference? 4:46am and cba to research.
301 is permanent, 302 is temporary
You'd use 302 to tell search engines that youre redirecting to a new page, but leave the old ones in the index because te page will ultimately be reinstated.
301 is permanent, so you're telling the search engine to redirect the user, and change its index to reflect the change