I have been using grunt calls for tha last couple years and really like them.The first series of grunts I will do is when I get into my stand.Any noise I make,whether its rustling leaves,snapping sticks or whatever I believe the grunt will settle down the deer thinking its another one in the area.
Alot of my grunt calling is blind.Meaning I dont see a deer in the immediate area but trying to get ones attention.At this time I will call maybe 5-7 times and put it away for about .5 hour to .45 hour at a time.I will try calling again and do the same.
If I see a deer then I dont want to over do it as he might pinpoint me to my specific location.When he is a distance away and not looking my way I will let out maybe 2 loud grunts to get his attention to come my way,if he turns his direction towards me then I will stop and get ready.I personally think grunt calls are a hit or miss situation,sometimes they are interested and sometimes coulden't care less.
To answer your question on the areas to use it,really dosn't matter.If you think the area holds a buck,then give it a go,besides what have you got to loose.