I went from a single to a double for the fact that they are more forgiving and in my opinion, sound better, also require less air.I'm using a Winglock wood/poly and it does everything I could want in a call.A single requires more air and you have to keep it crisp.It must be blown sharply. Try using the word "waak"or "vat" into the call, remember to finish the words.Don't worry about the hail, just get the basic quack first.Try this link, it should help a little;
http://www.ducks.org/waterfowling/ca...lling_tips.asp
Like I said, I switched to a double and am happy I did