Location is important. If you sit in your backyard you wont shool any ducks.
But it proves that ducks come to many wierd places in dusk.
After location come decoys, you will only get random chances if you dont use decoys. Calls eventually make your chances better.
Still you can select a perfect location and have a perfect spread of decoys. If you MOVE around when the ducks are approaching they wont come any near.
Actually, as a very experienced duckhunter, i would say, that the most important thing is to sit perfectly still and wait until the right moment to start aiming.
Ive seen many inexperinced hunters beginning to move their gun too early and in that way either scare the birds off or miss the best opportunity.
I have also tried, when i was retrieving a dead duck in the decoy spread, that a flock came in, and I got a chance, because I just froze and waited out in the open.