I've been using Framework Design Guidelines for a couple of months now, and reading Brad Abrams blog for longer. It's a great book BTW. Not only does it go beyond the usual naming convention standards, it let's you know what to expect from the .net framework and how to write code that works well with it.
One of the suggestions and also one of my pet peeves has to do with returning collections. You should always return a collection even if it is empty and never return null. Null doesn't add any information to the caller and just forces them to write extra code which has no real meaning other then handling an edge case.
That's my rant for now.
Thanks
Amen brother
That's right up there with "Don't throw exceptions for expected cases" such as, I don't know, Trying to load a business object by it's primary key, and it not being there. There's a case where throwing the exception gives you no more useful information than just returning null.