If you are planning to use Forms Based Authentication(FBA) for your SharePoint 2010 site, here is an excellent step-by-step procedure to configure so:
Update: For SharePoint 2010 RTM, follow this blog post: http://bit.ly/a5WhlE
HOW TO:Forms Based Authentication (FBA) on SharePoint 2010
The above link covers setting up FBA using Classic Mode Authentication. If you are looking to configure using Claims Based Authentication, you can refer the following blog post:
Configuring FBA in SharePoint Server 2010