Watch the birds' flight pattern. Are they headed your way or passing by? This determines your calling strategy and volume.
Use 3-5 honks at medium volume to greet the flock. Match the cadence of real geese - not too fast, not too slow.
If birds show interest (turning, cupping wings), continue calling. If they flare or ignore you, stop and let your decoys do the work.
As birds commit and get close, switch to softer clucks and moans. This mimics the sounds of feeding geese on the ground.
Stop calling when birds are locked in. Let the decoy spread finish them. Calling at this stage often flares birds.