Depends on where you're hunting. But every couple of minutes is usually about how often I'm calling, and it seems to work for me.

I don't even use a "predator" call. I use my Sceery Elk call. Just don't bite down on it, just give it a huff of air.

I agree with Jamesti, they lock in on your first screech and will come exactly to the call location if you let them. I have seen them lock in from 2 miles away. I have had them jump on my buddy behind my back and I've had one put his nose on my rifle barrel to give it a sniff after only one 5 second call.

Overcalling can be detrimental with a mouth call if you move to do it. They will be watching the call location even if you don't see them yet. Motion on your part will turn them quickly. If you have an electronic call, you can let it squeal until they bite it if you want too although I prefer to keep it quiet when I see them. I have had them leave for two minutes and then I hit it loud and they come back on the run.

Nomally, I stay quiet for about 20 minutes so they lose track of my location if they heard me approach. Then I blast for about 5 to 10 seconds. Then I keep quiet for about four or five minutes... trying this over about three times. I usually see them within seconds after the first blast if I am going to see them. Last month, I accidently activated my electronic call as I was setting it down. I shut it off instantly and looked up to see a coyote on the dead run 250 yards away. Unfortunately, he busted me out in the middle of a cut bean field and the jig was up so to speak.

If you don't see anything wtihin 10 minutes of your first call, it is time to check out another spot.