Multi-user Setup with Syndicated/Shared Database

Can anyone share how to configure a WP install such that 2 different domain names on the same server using the 3.0.x (MU) version of WP can run the same core software, share the plug-ins and share the same posts and comments from the DB.

I need to run 2 near-identical sites. I will use categories and tags to filter which posts land on which site, with some posts appearing on both.

So if anyone has done this, can you kindly share the install steps you went through or otherwise share links to the docs on how to do this.

I think I am finding that sharing the core software is achieved via “Networking”. I just need the complete picture and configuration steps to go through.

Thanks so much for helping.