There has been a thread going on at the RevitForum since 2012 titled 'Best Practices for Groups In High-rise Tower Models'.
There is some really valuable information that can be found throughout the thread from some very skilled Revit users.
It was updated a few weeks ago with a fairly lengthy summary (see page 3) of those best practice tips. It is certainly worth a read. Even if you aren't working on high-rise models, there are things in this list every Revit user should be aware of when using groups.
I really hope Autodesk are paying attention to this thread as well, because moving forward with development, some of these issues in my opinion need to be high on the list to fix.
You can find more information on groups from Ceilidh Higgins who did a talk at RTC Aus 2014 titled 'Get Your Groupon'. Aaron Maller also did a session at the same RTC, which I attended titled 'Abusing Groups in Revit'. A lot of what is covered in these handouts is mentioned in the RevitForum thread.
I will update this post if I come across further information about groups in the future.