Don't use anything open-source (or non-Microsoft for you .NET developers)
If Microsoft didn't develop it -- we don't use it here. Want to use ORM - EF, want to use IOC - Unity, want to log - enterprise logging application block. So many better libraries exist -- yet I'm always stuck ordering from the dollar menu of the development world. I swear every time I hear Microsoft Best Practices I think "McDonald's Nutritional Guidelines". Sure, you'll probably live if you follow them, but you'll also be malnourished and overweight.
- Note this might not be your best practice, but it's a common one followed almost everywhere I've worked.