I don't think that I am in total agreement with the majority of these posts and yet most of them also contain a grain of truth as well.
Here is my take:
In normal conditions from light until approaching overpowered, I move the cars until all three telltales (top, middle and bottom) break evenly. This is a cyclical process with adjustments being made to the cars and the halyards until the sail shape and the breaking points are right. As a broad generality, the cars tend to be slightly forward in light air due to gradient wind effect, tend to be set differently on opposite tacks when there is wind sheer, typically due to current or cold air over warm water or warm air over cold water).
Where I respectfully disagree with RichH is with twisting off the head of the jib in heavy air. While twisting off the head in heavy air is not a one size fits all solution, in my mind on a reasonably easily driven hull, it greatly increases the upper wind range of the sails. When I do this, I typically depower the jib, I have the sails set flatter and have the lower 1/2 to to 2/3 of the sail set perfectly for the breeze in terms of angle of attack and shape, and then have the upper portion of the sail twisted slightly open and flatter. This combined with depowering the mainsail pretty effectively reduces heeling and weather up until the point that a reef becomes necessary.
I understand that this means that the upper portion of the sail is not generating as much drive as it could, but by the time that I start opening the head of the sails, the boat typically has more drive than it can use. And while the head of the sail is flattened and twisted off, it si not so twisted that it is luffing.
Opening the upper leech of the jib not only reduces the heeling moment, it also moves the center of effort of the sail slightly forward. When combined with doing the same with the mainsail, the helm will get noticeably lighter. (In a fractional rig, this is one adjustment- tightening the backstay which straights the forestay which flattens the jib and moves the head of the jib aft slightly easing the leech slighly open, bends the mast which flattens the mainsail and moves the head of the mast aft which opens the leech.) Figuring out the proper amount of twist in heavy air is not all that hard. If you hold the helm while the changes are being made, you can feel the helm start to get more neutral and once the helm balances, where you want it, you stop. This is where adjust on the fly jib sheet leads are really helpful. (I have Garhauer infinitely adjustable jib sheet lead car on my smaller jib track and it works very well. I have Harken cars and tracks on the tracks for my larger sails and they work even better.)
I also am not a fan of reefing jibs by furling them, and see that as an absolute last resort. I have never seen a furled jib with as efficient a shape as an unfurled jib, (even those with sponge luffs or other ways of flattening the rolled draft), and while the sail is not so terrible when furled to something less than 10%, after about 10% of the sail area has been rolled, the furled shape only gets worse and frankly starts chasing its tail ( i.e. the sail providing progressively less drive relative to its drag and side force with only the best of bad choices left).
Below are a couple shots showing the jib twisted open to reduce heel and helm angle. In the second shot, I am still adjusting the traveler and mainsheet.