I call every 10 to 15 minutes - during pre-rut, rut, early post-rut I use a mix of buck grunts and doe bleats - trying to make it sound like a doe is being followed by a buck. I will blind call as I have had luck in getting bucks to come into an area based on that. Louder the better if calling blind - want all the area to hear and possibly respond. I have called at does when hunting as well - mostly they don't seem to care, does not scare them but does not draw them either. I did call in a sighted buck once but almost blew that because I used a doe bleat - he stopped and looked but did not see a doe so kept walking - I then let out a loud buck grunt and he came in looking hard for the opponent.
"don't stink, don't move, don't make noise"