First be careful to chose an easily readable facsimile. It's more important than you might think at first sight, since my experience has been that the bad condition of a document may lead to more problems than the transcription rules themselves: some continuation signs may refer to various places on the sheet, some notes have been emendated, some note stems are hardly visible, some rests may look like points - or conversely - all these problems can be real traps for the beginner that we still are at the present time!