Get the sail to pull not push!
The non- sailor believes the mechanics of how a sail ALWAYS works is that the wind pushes the sail from behind to make the boat go. This is only true in RUNNING down wind with the wind behind you pushing, you can only go as fast as the wind minus the water resistance on the hull and then for you to get back home you will need to find a spot on the water where the wind is coming from the opposite direction, this is the way the old square rigged clipper ships worked in the 1800’s.
The modern day sloop rigged boats work the mechanics of nature by using the wind to pull on the front of the sail to make the boat go. To pull not push! To pull the sail you must have wind on the sail front. Sounds crazy, but that is how a modern day sail works.
Take a letter size piece of paper and grab two side corners one in each hand, holding them level about a foot from your lips. With the two corners level the paper bows out away from you and bends down till the other two corners are pointing towards the floor. Blow real hard over the top of the paper!
Now, to get the wind moving over the front of the sail you need the first 12 inches of the luff or the leading edge of the sail to point dead into the wind, wherever it’s coming from. So, letting it out or 45 degrees is close but, not exact. The ideal spot is when the wind is equal on both sides of the sail, if one side it’s stronger then the other side of the sail will stall a little bit, reducing pull.
You have two indicators of where that sail should be, telltales and the feel of the helm!
If you learn to use the telltales the feel of the helm will come to you over time.
Headsail
The material your head sail is made from is semitransparent so that a length of dark ribbon or yard about 10 inches back from the leading edge can be seen through the fabric. When both of these telltales are streaming backwards the leading edge is pointing dead into the wind. If one of these telltales is flopping around then you do not have enough wind on that side of the sail.
Place one tell tale on each side of the sail up as high as you can see from the helm under the mainsail. Make sure this tale is light in structure so it will move in the wind. Placing other tell tales can be done later when you learn how to use them to tune the whole sail or rigging.
As someone stated, when they race someone is always adjusting the sail. For you now, set your point of sail, adjust the headsail so both tales are flying back and then steer the boat to keep them both flying till you make a turn to go in another direction.
Don’t worry about tales on the mainsail, after you figure out the headsail placement for the direction of the wind, let the mainsail out till you see a little belly in the main right next to the mast, then pull the main in till that belly is gone.