Proximity to a roost, good cover, loafing areas, a range of food sources to provide for different species and weather climates.

Flyways are flyways for a reason... they have a flight path where there is consistent sources of what I listed above.

Food source and be on a local flyway. I have holes you can run traffic on 7 days a week, and I have holes that arent on their flyway that I might only hunt once every other week because the ducks have to go out of their way to find it, and then you have to wait till they bring enough of their friends with them to have enough numbers to shoot. Remember puddle ducks can only feed as deep as they can dip. So if your hole has only about 2 or 3 ft of shallow water before it gets deep then your food source is limited and wont take long until its peeled off and the ducks go somewhere else. Ducks will follow draws, creeks, rivers, and even powerlines coming from their roost. Google earth your duck hole and see if you have one.