Try not to get frustrated! Sometimes they respond and sometimes not, in fact, if they're not in the "mood" to respond you'll probably be spooking them. I've rattled all day from spot to spot and seen nothing then the next day a big buck will come charging in...so you just never know.

I usually rattle for a few minutes, bang/scrape the antlers against a tree, throw in a couple grunts (bleets may make it sound like they're fighting over a doe), wait for 15-20 minutes or so and go at it again. If I get no response in 45-60 minutes I'll stop. Then I'll either stalk and maybe find another good vantage point to call from or if I'm just calling that day I'll drive to another calling spot.

Don't worry TOO much about hiding yourself; afterall, if they think there's a fight happening they will expect some movement! However, if you see a deer responding you can stop calling...it's done it's job! Maybe a grunt or two at that point wouldn't hurt.

Hope that helps a bit and good luck.