I like to use the "three-bunch rule" when attempting a pass-shooting ambush. Geese tend to send out scouts before the larger concentration flies out in one or two flocks. When three small flocks take the same vector -- like over a lone oak tree or the ninth fencepost in a field -- move posthaste to get directly under this vector, hunker down and stay still. Don't take time to set out any decoys. Decoys can be counterproductive when hunting close to a "refuge" area. The honkers know where they can safely loaf. They aren't about to slide into an area within a mile of their sanctuary to "visit" with your plastic geese. Ditto with calling, no matter how good you think you are. The geese know their plastic cousins weren't there last night. They don't want to hear you trying to convince them that all is well and breakfast is served, either.
Decoys have value when setting up a stool more than a mile from the sanctuary, especially if you're fortunate enough to be in the chosen flight path for the day. As soon as you see them coming, get on the call. Try to find the fine line between being aggressive and overcalling.
Something that has been a source of perpetual amazement to me is how Canada geese all seem to choose a particular vector, even if there are no other geese in the sky to follow to their chosen feeding destination. Is it because of subtle nuances in the wind? Is it visual, as in the lone oak tree or fact that the ninth fencepost is on high ground or in direct line of sight with another lone oak tree that geese can see once airborne? I don't know. But I do know that you don't want to ponder this question once the third bunch has lifted off and followed a particular track to their feeding destination.
Use any available cover that is under the bird's flight path. If no cover is available, lie low and hold perfectly still while looking at the ground until you hear the "woof woof" of wings overhead. A big, shiny pumpkin-pie face intent on watching the panorama of goose flight ensures an emergency course adjustment by your quarry when the geese are still out of range. The only advantage of having a swivel-headed hunting partner is the money you'll save on shotgun shells. So get ready, hold still and look down. When you hear wings, jump up and establish your lead, double it, add a foot, and squeeze the trigger.
Do your homework and you can work up an appetite for breakfast by toting a heavy bird strap back to the truck. Or you can take the time to run a victory lap around the bases!