The eventual goal for your upwind development is to be able to sail to windward by merely feeling the boat. However, in the beginning, and also in some conditions, such as very light air, you will need to watch the telltales on the jib (or the main if you’re in a cat-rigged boat, like the Laser). Have the crew pull the jib in as far as possible. By “as far as possible,” I mean the point where it is as close to the centerline of the boat, without “squashing” all the power out). Don’t flatten it completely. To determine where this point is, sail against someone while trying different settings on the jib. If the boat feels sluggish, let the jib out a little to put some power back in. Remember, also, that if the jib is cranked in too tight, this will close the slot between the jib and the main.
Once you have the jib trimmed correctly, you can start steering the boat, using the telltales as guides. If the outside telltale “piddles,” this means the sail is overtrimmed for the direction of the wind on the boat. You don’t want to let the sail out, so you must head up. This, in effect, retrims the sails, except instead of bringing the sails in, you “brought the whole boat in.”
If the inside telltale piddles constantly, or if the sail luffs (actual luffing, or just an inversion at the front edge of the sail), the jib is undertrimmed. You don’t want to crank in more on the sheet, so you must retrim by bearing off.
Your goal is to make the outside tale flow straight back and the inside tale “lift” occasionally, meaning some air is getting to it, but not all the time. If you don’t know how often the inside tale should be lifting, err on the side of too often. It’s better to have too much air flowing along the inside edge of the sail, than not enough.
When this happens, you should be pointing as high as possible. Remember through all this adjusting that if the boat is not up to speed, you won’t be able to point, so make sure you’re going as fast as you can. Also, you should be able to feel when the power is gone from the jib and the main.