Change your WordPress Permalinks
In the good old days, when changing your Permalink structure (i.e. how the URLs look) in WordPress you’d need to amend the Apache .htaccess file (or equivalent) to cater for the appropriate 301 redirects (a 301 redirect states that the URL has permanently been moved to a different address which is provided). Human understandable URLs are important for Search Engine Optimization reasons. There were numerous ways of doing this 
including a few WordPress Plugins however the most reliable was amending the .htaccess file directly. This whole process and the ramifications of either getting it wrong or not doing it at all created huge sales for Paracetamol sellers (i.e. many headaches were created).
Resolve WordPress Permalink Headache
Recently I have needed to change the Permalink structure for a client running a WordPress 2.7.1 blog. The Permalink structure was ‘/%year%/%monthnum%/%postname%/’ and the new structure ‘/%post_id%/%postname%/’. I spent hours investigating how best to enable the appropriate 301 redirects and went crazy with finding all sorts of conflicting information so I decided just to test changing the Permalink structure in a test WordPress 2.7.1 install.
WordPress does 301 Redirect
The result: no need for any stress as WordPress handles the 301 redirect for you. You see, those clever people over at automattic (the people keeping WordPress and other great software running) have automated the whole 301 redirect issue; now there is no need for redirect plugins nor amending the .htaccess file. Change the Permalink structure in WordPress and the 301 redirect will be created for you! Happy days!!!
Jun 22, 2009 @ 12:37:29
I tried doing this myself on one of my WP blogs and it doesn't seem to work. If I change link link (want to have just the postname, after a matt cutts post suggested doing so), it shows a 404 error.
Any ideas what the problem is?
Jun 28, 2009 @ 04:05:12
nice simple, im looking into does hosted WordPress.com blogs also do the auto 301 redirect for permalinks.
one point which makes the 301 redirects work better is to run a linux server that allows the htaccess file to be enabled, otherwise it does have some limitations.