do your reasearch with local hunters and the internet on the type of ducks in your area. Observe ducks from shore or a boat before season on there flight from resting to feeding areas, and getting out while it is still dark and waiting is the best time also right before dusk.I would suggest starting with 3-4 dozen decoys.If you plan to hunt near shore i would suggest 1 doz. of those to be mallards and place them nearest to shore.
You want to set out your decoys in a j shaped pattern so that ducks fly in from the top of the jay and follow the line down int the hooked part, this is wear they wnt to land if the wind is right, try to set up so they land int the wind, also set up to one side of the hook, not the bottom so ducks arent looking directly at you. you should start to practice calling . hope this helps.
15 Green Wing
5 Wood Ducks