Depends on the talent and the mic. I use one closer (1") on an RE-20, further (2-3") on an LDC like an AT 4047. Also, you can usually get closer with a metal-type of screen (Stedman) than a nylon Stoppit.

I just generally put my smelly old pantyhose right over top of the microphone. That way, if the singer gets too close, they will know to back off instantly! Problem solved! Just ask your girlfriends/wives for some but only after they have worn them for about a week.

Peculiarly pungent
Ms. Remy Ann David

In this case remy, the nose knows... :D