This was originally written in response to Dale Phillips question posted on rec.boats.racing. I've modified it slightly (and tried to correct some of the more obvious spelling and grammar problems...;-)
Shroud tension low - under 200 lbs (I should point out that some other people use high rig tension to flatten the upper main. I like to keep the jib luff "soft" so it is easy to read).
Mast pre-bent to flatten sail, particularly the entry, as too much fullness forward in the main closes the slot between main and jib. I believe mast bend can be critical in these conditions. Too little bend gives you too full a main. The result is poor pointing and mediocre speed. Optimum mast bend gives you the same speed as your competitors, and a little more pointing. Too much bend, may also result in poor pointing. Eyeball how much mast bend competitors with the same type of sails are using before the race. Tune up with someone before the race, and experiment with mast bend.
Vang to control the leech of the main. The top leech telltale on the main should fly some, but not all of the time (maybe about half the time). The flatter the water (less wave or chop), the flatter you can go on sail shape, and the higher you can point. Main on centerline. When the wind is ridiculously light, ease everything and just try to keep the boat moving. In very light, the weight of the boom closes the leech of the main. Don't add any vang or mainsheet tension to make it worse.
Sheet the jib reasonably close, but not so as to close the slot. I put a jib leech telltale where I can see it through the upper main window. I never stall that telltale unless I'm desperately trying to claw up from a boat on my lee bow. If you have flattened the main entry, you can sheet the jib tighter than otherwise.
Sail heeled a little and high (inside telltales lifting some of the time) in the lulls, and flat and not as high in the puffs. Pay attention to the leeches of both sails. In any decent puff, you may wish to sheet the jib half an inch or so tighter, and put a little more leech tension on the main using either vang or mainsheet. Ease jib and vang as soon as the puff dies. Crew sits inside as far forward as possible, skipper as far forward as possible (against shroud); use a telescoping tiller extension so you can sit further forward.
Once the breeze comes up so that you are close to using the trapeze (assuming typical crew weight), you can power the boat up by straightening the mast, and using rig tension (250-550 on shrouds) to keep the jib luff from sagging to much (that hurts pointing). You power the boat up earlier if you are being slowed by waves or chop, later if you are in very flat water. If anyone has a crew on the wire and skipper sitting on the side tank, you should be moving to the power settings rather than the light air point settings. Inner telltales fly up (pointing too high) rather less than half the time (when you're pointing up gently to make sure you're on the wind). Keep pointing high though, as you give away more height than you gain back in speed when you foot.
Mast bend is critical in these conditions. Too much, and you do not point. Too little, and you are underpowered and also not pointing.
Sheet jib to same place as light air, use vang to keep main leech from twisting too much. The jib leech may have to be a little more open to accommodate the fuller main entry. Main on centerline. Hike hard in puffs to keep boat flat.
Remember to ease the vang and get the board up BEFORE you try to bear off around the windward mark.