I often get asked about how to go about customising a WSS/MOSS master page.

Here is the advice I give:

1. Don't for the love of the children try to write one from scratch! You will end up pulling out your hair and banging your head against a brick wall. Start with one of the out of the box ones, and remove/change the bits you want.
2. Start with the Minimal.master page up on MSDN. This is a very basic bare bones master page. It has everything you need in a masterpage, but no look and feel. You can then go and add everything you need.

Get it here:

How to: Create a Minimal Master Page: http://msdn2.microsoft.com/en-us/library/aa660698.aspx