Never really got into hunting geese only, but have shot them while duck hunting over the years. lots of ways to hunt ducks, early in the season the smaller ducks are around, woodducks mostly, if you go watch a pond or river during the evening you will see where they want to land, set up in that area in the morning and you will have some good pass shooting, no need for decoys just take a call with you (mallard or woodduck) when you see them just give a couple of calls and wait. pass shooting woodducks can be a humbling experince, they are fast. another way to get them is to walk a slow moving creek, you will find them in the pools, they are much easier to jump shoot.
later in the year, late November or December we hunt the bigger ducks, (blacks, mallards). we use decoys and call them at that time of the year, they are tough to call sometimes educated ones will make 4 or 5 circles to check out your spread. decoy shapes this time of year should be in a C or a Raft. i do better with the Raft set up that time of the year. 30 to 40 decoys.
once you get into it, ducks are easy to identify. i only shoot winchester steel shot. #4 mostly.