I just went through this last year - how to call ducks...

The caller we had got through cancer and they removed his tongue - yes DAMN! .. he is a good friend, it was hard on him... still puts me back.

Anyway -

Out of all the advice I got, here is what worked.

You need a call that isn’t crap to learn on -

1). I bought a bunch (tried a bunch), Zink’s ATM green machine was by far the best deal, that had the range needed.

2). Second - you need a instruction CD that breaks things down the science of the sounds, and how to make them -
Here you can’t beat Carlson’s Champion calls - duck calling A to Z.

These 2 are what got me to be proficient... after that it was hunting, and driving to the lake to hear the ducks sounds...
the CD will tell you when to call & shut up - it has a DVD in it where they show the birds reacting to the call, and when not to call.