"OK Luff, got that what's the next most important thing after keeping the boat upright?" asked Tingle.
"I think I would say watch the wind. If you stand on the Clubship and watch a flag you will see it keeps moving from side to side. The wind has a general direction but it blows slightly to one side of that for a while then slightly to the other side. Also the strength is not consistent it will blow slightly more strongly then slightly more softly. It is doing this when you are in the boat so all the time you must be either adjusting the sail letting it in and out as the wind changes or if the sail is cleated steering the boat to change her angle to the wind." When I have old Stumpy Winder crewing for me I never let him cleat the genoa I expect all the time him to be winching in, letting out, winching in as the wind changes. If you are racing and there is another boat in front of you the most likely reason is she is spotting the wind changes and adjusting her sails or course quicker than you are.
"So how do you tell when the wind changes?" "Well there are lot's of ways, some depend on the boat you are sailing, the first book I had on learning to sail, one about learning to sail on the Norfolk Broads had 'Watch the burgee' in big letters at the top and bottom of every page because the author thought it was so important. If the boat you are on has a burgee you can watch that, if you are sailing a Thames Barge that is probably exactly what you would do, stare at the streamer at the top of the topmast. On a dinghy you may have telltales on the shrouds (chiffon is good) which will tell you a lot. On my cruiser you can sail to windward on the electronics, every time the needle comes off 30 degrees to the apparent wind steer the boat to move it back. Most modern sails have telltales sewn in the ones on both sides should be streaming back. When you are steering a straight course they are very good for telling you the wind has changed and the sail needs adjusting. You can watch the luff of the sail, if it starts to fill from the back the wind has headed you and you need to sheet in or pull your helm up to bear away. It's harder to spot freeing shifts with the sail, you need to keep checking the sheet a little till you just get a slight judder on the luff of the sail. You mustn't forget as well feeling the wind round your ears and watching the ripples on the water. Particularly watch the ripples upwind, if you can spot a windshift coming you'll soon be sailing faster than the other boats.