I'm doing the same thing right now...I've found to minimize tape use and maximize time, setup the master shot for the rehearsal and record their first couple of passes through the scene. You won't use the master as much as the singles (
http://www.yafiunderground.com/Tutorials/index.html ).
Then have each actor deliver their lines in the singles...if they or you don't like the way it's coming out or the way it's written...have them pause reset their composure and deliver the line differently. The singles don't have to be full read-throughs of a scene as you'll be editing just the best parts anyway.
Then reset the camera for the other actor's singles and go again. The offscreen actor can deliver their lines from a chair nearby unless they are in the shot for an over the shoulder (OTS) type of shot. Concentrating more time on the singles will get you moving faster in your shoot. If you end up really strapped for time or tape, you can pick which lines will be used in master for editing and have the actors do just those lines, then do the full scene scene in singles (even the parts that will be in master so you have the better sound as you can mike more closely in the singles).
If you have certain parts as you're going through the singles that should have closer shots, put a check mark by the line in the script and when you finish with that person's singles, just tighten up the shot to get the emotional marrow from their performance. When you capture the footage later, have the script next to you so you can remember the marks in the script as they relate to the footage.
Label all your tapes!!!! I only did day-tape numbers and I'm kicking myself.
I'm putting an extensive how to guide to the pre-post production parts of film-making (I'll leave the budgetary stuff to others) up at my website (
http://www.yafiunderground.com ). It's under the current link on the left...but I'll be moving it to a tutorial link later.
Hope That Helps