Buck Grunt and Doe bleats, change the use and tone with the changing phase of rut. I suggest getting a video or tape to help you mimic those calls. Their use to be a website that had buck grunts on it, maybe someone here can post it, I use to have it written down but can' t find it now.

I say keeping 70% of your calling to visual calling, meaning seeing a deer before you call. I do blind call with a grunt only when rattling and sometimes blind doe bleat as taz suggested. I also hole heartly agree if he is coming shut up, the most common mistake is over calling!!!! If you do blind call make sure to space the call atempts out to 20 min - 30 mins. Then only exception would be if rattling in rut, then 10-15 minutes which should be your rattling break half way point, should be implemented. During rut is absolutely essential to keep a bucks attention, one lull and he is off in a different direction.