Hunting ducks and geese is no different than hunting a deer or an elk.  You really need to scout the out and see where they are flying too and from, along with what times they are doing it.  They live on water but will feed in fields but if the fields are private and you can't get permission to hunt on them then you need to find a place inbetween that you can intercept them witch isn't easy since they will be heading to their feeding area and unless you are in another feeding area they won't pay any attention to any decoys that you place out.  Also other hunters need to be figured into the forumla.  If they are spooking them or hunting in the feed field then you may need to go elsewhere to find them. 

Need a little more info from you.  Like where are you hunting(state)...just curious.  Also will you be hunting them on water, ice or what kind of feeding hill?  How far from the roost are you?  What is the surrounding pressure like?  Weather can play a big part in how decoys are set up.  Type of feild can also play a part....nioce flat field or a rolling field.  I am nore than willing to help ya out just shoot me some more info and I will help you the best I can.

You need to scout the area for a couple days in a row at least.  Get an idea of approx what time of day the birds are flying into a certain field.  Look for cut grain fields anything with seeds or cernals.  Water doesn't nessesarity have to be right next to the field, but there should be bodies of water in the area within a few miles.  Good luck.  I've said it before and I'll say it again - my boots, maps, and binoculars get way more use when I'm not actually hunting, but scouting.