I just completed a single drawing that has four layouts in it.  I have a plan view, two layouts with elevations, and a detail sheet.  I did it this way because it seemed easier than creating four separate drawings.  I think it is up to the user to decide what works best for them.

What's the correct order of things re: layers?  Not exactly sure what you are asking.  What field do you work in?  Do you work for yourself or for a company? 

Each company has its own way of putting together a set of drawings.  Approach it logically in terms of how the building is constructed.  You wouldn't start off with the roof plan being the first sheet now would you?

Typically I do go with this order: site plan, foundation, plan view, elevations, sections, plumbing, electrical, roof plan then a couple of pages of details.  How do you do it?