I found the raspier the call, better. A whistle is good for calling teal, pinnies and widgeon. They have the combo whistles. Mine will do a mallard growl too.
A good set of dekes with their heads up work better than the hot buys. most of the HB's are sleepers.
The ducks know their buddies don't land and snooze., especially if you are calling and all your dekes look like they are asleep.
It's good to have a few surface feeders too.
Most ducks flock with their own. The lesser ducks, teal, widgeon, and spoonies, will come into where mallards are. Pintail are the most wary. they circle and look a long time before they will commit.
good luck
If it's brown it is down.