Whatever you do Ozzy1, don't do what is seen at our workplace, where the first release is at "IR" as in "Initial revision".
Files get sorted on the hard drive in alpha-numeric order so strange things happen.
It hasn't happened yet, but some rookie is going to come along and forget the other rule that you skip revision "I" between rev "H" and "J", and the confusion will get even worse.
My personal preference is to make sure the revision is a letter, and keep drawings ordered solely by number. If the drawings are organized with alphabetic designations, then a number to track the revisions stands out more. Letter drawing names invites wild imagination into file name conventions so avoid it. Make sure to use computer file names that equate the file name to the drawing number and revision. Do it in a way that the operating system can naturally sort them in a reasonable order. Do this even if you have a data management system or database that tracks this for you, because somebody has to manage the database.
It is not difficult to create a system that tracks, and isolates, the preliminaries that have been released before the drawings are approved. If the company has a data management system database, this may be an impediment to issuing prelims, but on the other hand, the prelims don't have to be made distinct from the approved drawings, if there is a "master drawing" or list that defines at what revision status each drawing becomes approved. Implying that any earlier revisions were not approved, just drafts.
STF