simple domain redirection

[Stuwoo]

This must come up all the time, and having spent a few hours searching across the net, I'm baffled by the mod_rewrite.

I have two domains pointed at the same site and I want to stop using one of them. However I want search engines that have spidered the old domain to find the replaced domain.

SO www.mydomain.com/somedirectory/thisfile.php
would change to www.mydomain.net/somedirectory/thisfile.php

The site structure is the same - as both domains point to the same site.

I could point the old domain to a subdomain and then use mod_rewite?

Any ideas, I'm sure this has come up sooo many times