We place our objects in model space at full size. We then switch to layouts and insert our title block and border, add our notes and dimensions. Some people put everything but the title block and border in model space (annotative text and dimensions helps in this regard). There is no "right" or "wrong" way. Each has its own strengths and weaknesses.
We seldom use Xrefs so I will defer to other more frequent users of that particular function.
I'm not sure about your question regarding revisions and master copies. Are you asking how drawings are controlled? Again, it depends on the size of the company, the number of drawings, the number of CAD users, etc. One option is AutoDesk's AutoCAD Vault (it's a freebie). Further information available at the AutoDesk website.