Download the WordPress MU Sitewide Tags application from
http://wordpress.org/extend/plugins/wordpress-mu-sitewide-tags/.
Upload the plugin to your
/wp-content/plugins
folder.Enable the plugin via the Site Admin panel.
Go to Site Options, scroll down to the bottom of the page, and check the Tags Blog box to enable tags.
Check the Tags can be indexed by Search Engines box.
Make a post or two on your test blogs, and then visit the tags subdomain for your site; you should see something like this:
We have just set up an improved tagging system for our users. The WP Auto Tagger plugin pulls out words that it thinks are important from blog posts and uses them as tags. The plugin isn't perfect and it does sometimes come up with silly suggestions, but users can remove tags that they don't want, or replace them with their own.
The Auto Tagger plugin ensures that even users who don't take the time to pick out their own tags will still have the option...