I'm no expert and I've no interest in promoting the company, but I was really impressed with the clean way this new Revit sash window family was created and documented by the man from revitcontent.com
http://www.revit-content.com/content...ndow/index.htm
I have made my own families to do this sort of thing but they are pretty messy and have various limitations.
I don't know if I would want to buy everything they do but even just as an example of family creation some of it is worth a look I'd say.