Don't put too much hope in calls. While they do have their place it's not the most important thing. The week or two leading up to the rut is the best to use grunts and rattling. I have a Buck Roar call by Primos. It is a very good grunt call because it's realistic and louder than most. I use calls most time to "lure" a buck in that I have seen at a distance. If they are in the right state of mind you can call them in with a few grunts or hitting the horns a little. Don't over do it. It's not like calling in a turkey.
The most important thing is to hunt as much as you can. The bucks will be out at all times of the day looking for does. Go where the does are. Also believe it or not I have better than average buck sightings on windy days as the rut starts up. I believe it may cause the does to hold up in beds and the bucks will be out looking harder to find them. Just put in a lot of time and something good will happen sooner or later.