Because the wind rarely comes from a consistent direction for very long, big advantages can be achieved by being on the tack that takes you nearest to the windward mark. Changes in wind direction tend to occur during gusts and lulls, and keen-eyed sailors will see their effect on the water before they arrive. With good communication between the helm and crew you can be ready to tack if the wind heads you (takes you further away from the windward buoy) or turn upwind a little if the wind lifts you (takes you nearer the windward buoy).