Anilrgowda

You've got a site that needs a new domain. Maybe it's a rebranding issue, or maybe it's a folder or subdomain that has outgrown the current site. There may be dozens of reasons why your currently indexed and well-ranked site needs a new domain name.
Unfortunately, Google doesn't seem to recognize that you've simply changed the URL of an existing site, and ends up subjecting the new domain to the aging delay as if it were a brand new out-of-the-box site. It doesn't seem fair when you've struggled to earn the rankings you have now! You really can't afford to lose the traffic you already have, but there is a real business need for the change. What should you do?
Permanent Redirect Not Always the Best Choice

Conventional wisdom will tell you to redirect the old domain to the new domain using a 301 "permanently moved" response. This tells the engines that the old URL is no longer going to be used and the new one is the correct one, so that they can update their index with the appropriate URL.
However, if you follow this usually accurate advice, you'll find the new pages do not automatically assume the positions of the old ones in Google...they will remain off the chart. Even though you are telling Google that this site is exactly the same as the old one, the aging filter will still apply. This doesn't seem like the best strategy, as your site will remain in oblivion until it ages properly.
Temporary Redirect is the Way to Go

By using a 302 "temporarily moved" response instead of a 301, the original URL will remain in Google's index, and maintain its position as if the page were still there. However, visitors who click on the link will be brought to your new URL, exactly where you want them to be. It's the best of both worlds -- you retain your rankings during that interim aging period, but visitors are redirected to the updated and correct domain.
Once the 302-redirect is in place, it's imperative to start a linking campaign for the new site. You'll need links pointing to it in order for it to be ready to rank well when it's released from the aging filter. When you notice the new domain starting to show up in the rankings (anywhere from 6-12 months, typically) then it's time to contact your previous linking partners to update their links from the old domain to the new one.
The Final Move

Once the new domain has properly aged, go back and change the 302-temporary redirect to a 301-permanent redirect. This will transfer the link popularity from the original site and finalize the move to the new domain. It's a good idea to retain those original pages at the old domain until you are reasonably sure all the links around the 'Net have been updated with your new URL.
Moving a site can be a real pain, but by following this strategy you won't have to sacrifice your hard-earned Google rankings while waiting for the clock to tick.