Learning to use one of them things is all about literally holding your mouth right.Most diaphram calls have a top side, sometimes marked with a raised spot in the metal frame under the tape. This should go towards the roof of your mouth. The latex reed should face your teeth and the horse shoe shaped portion goes towards the back of your mouth. One of the things to get used to is having the contraption in your mouth, saliva wells up in my mouth something fierce when I first start practicing with them again. Different calls have different thickness, texture, and *gag* tasting tape. If one type doesn't seem to do it try another brand. To start its a good idea to just get used to having the call in your mouth, dont worry about blowing on it just take it in and out of your mouth at intervals based on your need. A good seal must be made with the tape, the roof of your mouth, and your tongue. Another thing to get used to is the vibration created by the reed. You may need to cut the tape or use a smaller framed/youth call based on the way the call fits the roof of your mouth.The idea is to force air across the latex to create the sounds. The hard part is figuring out the amount of air, where to keep your tongue, and what to do with the slobber. It is all trial and error based on your mouth and the call. I push up against the taped side section of the call with the back of my tongue creating a seal with the tape between my tongue and the roof of my mouth/teeth. You might have to drop your jaw and purse your lips some to stiffen your cheeks to keep the air from pushing your cheeks out.There are many National Wild Turkey Banquets and shows going on, normally at the shows there will be every call maker you can imagine. Great place for a beginner to get some tips and sadly an even better place to get overwhelmed. Another place is the BassPro Shops Spring Fling or whatever they call it...I'm sure Gander Mtn or other companies must do something similar this time of year where they have call makers come in and demo calls.Start with calls with single reeds and no major cuts as they tend to be easier to work, then you can work your way up to double, tripple, or more reed calls and those that have specific areas cut for sound pitch.You might try this site/video:
www.theamericanoutdoorsman.com/WSTH.htmlor this sites description:
www.turkeyhunting.com/hunting/calls4.asp