There are many ways to rell the direction of the wind. Wind blowing across water causes friction on the surface, forming small ripples perpendicular to the direction of the wind. Learning to determine the wind's direction by looking at the water's surface takes much practice, but it's the most accurate method. Other heopful indicators are flags, smoke, and other sailboats. There are a couple of simple tools that can help you find the direction of the apparent wind.
Telltales are lengthsof yarn or strips of nylon tied to the shrouds and backstay.
A masthead fly, with a wind arrow, goes at the top of the mast and points into the wind. You can also use your sails to find wind direction. When you ease your sails, they will luff and line up with the wind. This occurs at around 12 to 14 knots , a point at which many small boats begin to get less stable. Inexperienced sailors shouldn't be out alone when there are whitecaps.