Someone asked me about this the other day - there are currently no concrete set of guidelines for unit testing best practices (not talking about HOW-TOs, but about HOW_NOT_TOs). So it occurred to me that I've been keeping such a list on this blog for a while now (I keep adding whenever I get the time to post something new to it) only its buried on the left side of my blog page.
So, you can get the full list here:
http://weblogs.asp.net/rosherove/archive/tags/Testing+Guidelines/default.aspx
There's also an RSS feed especially for that if you'd like on that page.
I'm working on publishing an article on this topic (some sort of a top-10 tips for better unit tests) for MSDN Magazine so I'm holding off some of the content, and it's killing me I swear. Hopefully it won't be long now.
This Monday (August 1st) I'm heading off to Ireland to do some training over there. I'll also stop by at the Irish .NET user group and give two talks: intro to Agile development and Unit Testing Best Practices (more elaborate than the category I just linked to + some new stuff)