The sailor must constantly monitor and be aware of wind direction. When arriving at a body of water, determination of wind direction and speed is the first thing the sailor will do. The boat will be pointed into the wind to be rigged and a plan will be formulated to launch the boat and start sailing. The direction the wind is blowing from (not to) is designated as the direction of the true wind.
There are many ways to determine wind direction. Face the wind, and then turn your head until the wind is felt evenly on both ears – your nose will point to the wind. Check the direction of smoke coming from smokestacks. Drop some grass and see which way it moves. Look at the ripples or waves on the water. Note the direction that flags or pennants are blowing. Examine the direction of telltales (small lengths of wool, nylon or other lightweight material) attached to standing rigging or a masthead fly. Also, boats tied to moorings will point into the wind.
When the boat is rigged, the sail provides an excellent means of determining wind direction. Point the bow of the boat somewhere toward the wind. Allow the sail to move with the wind and it will act like a flag and line up so that the luff edge points in the direction of the true wind.
The above article is from Thomas P. Martin's excellent book, Sailing is a Breeze: Learning to Sail a Laser®, Sunfish® or Other Small Boat. You can save 20% by ordering here!
Author Thomas P. Martin