For the earlier versions of Joomla like Joomla 1.5 , 2.5, you had to do the changes in the .htaccess file. But with that, there is a problem . Lets say, you website needs around 1000 of 301 redirects . So, if you put those 1000 requests on the .htaccess file , the website just takes a bit of time to resolve, as it has to look all through the .htaccess file .
Thanks to Joomla 3.0, for their nice addition called REDIRECTOR MANAGER.
You can find it under the COMPONENTS drop down.
Select Components → Redirect from the drop-down menu of the Joomla! Administrator Panel.
Its pretty straight forward to use .
Simply click on NEW , Enter your old URL and enter your new URL. SAVE it and you are done!