Pilot - You've got some good advice on here so far.
I carry box, pot and peg and mouth calls every time I hit the woods, and many times use them all, depending on the hunt of course. The best thing to do is practice them all until you get proficient on each, and then practice them more, until you get even better. Then, practice some more. [;)] You can never have to much experience running any of your calls.
Creek - I'd suggest posting your question up on a different thread, so you don't end up hijacking this one, and you might get more advice if it's not buried in the middle of a different question.
If the only prayer you said in your whole life was, "thank you," that would suffice.