Without placing the call in your mouth....press your tongue up against the roof of your mouth to block off the air flow your trying to push out from your diaphram, not necessarily blowing but forcing out....allow some air to flow over your tongue and then drop your jaw creating a sssssyyyyaaaa practice that like a yelp.....remember that, now place the call in your mouth practicing the same technique. Force air over the call, do not blow and create the yeeeeellllll, drop the jaw llllpppppp pick up the rythm....yelp, yelp yelp....some say the word raup, raup, raup...trying to put down in words how to use a mouth call is very difficult....keep practicing.