SharePoint Services v3 – Change Control / Mgmt

What are the best practices for controlling changes to SharePoint Services v3?

Here are a few questions:

Do you recommend keeping Dev, QA, UAT and Prod in synch? Do you recommend a mirrored prod environment?

Do you recommend doing changes directly in Prod?

Do you recommend having one test environment instead of QA and UAT?

What migration tools do you recommend?

Basically, I am looking for SharePoint’s best practices for making any type of changes…whether it’s code or configuration changes.

Thanks,
Scott