I keep reading quotes like:
“Before combining subtools be sure that your computer will be able to cope with the polycount of the combined mesh. This must not be greater than the maximum for your system.”
Does anyone know where I can find a table explaining the comparison between RAM and polycount?
I am currently running 6Gb of RAM, but can’t be sure on the polycount settings under preferences.
I think most of us do this on a trial and error basis and get a “feel” for it. I’ve never seen it as an exact science (although I’m sure it is), but usually once you get into ZBrush you develop a kind of intuition for these things.
That’s as helpful as I can be I’m afraid 
Thanks Eastman
I’ll just carry on as I am. Use my intuition, which I find is working. I just thought there might be something in B&W.