I agree with the previous post. As a general rule, the jib should be made to break evenly, and this is usually done by moving the jib car forward (to get the bottom telltale to luff first) or aft (to get the top to luff first).

In addition, if your boat is set up with inboard/outboard jib cars, these should be set proportionally to the main traveler. I.e., if you travel out the main 6" from center, you should travel out the jib car a few inches from it's inboard position.

The jib should also be made to match the mainsail. So if the top of the main is twisted (top telltales luffing) then the jib should be twisted (with the top telltales luffing).

I usually depower by travelling out, twisting (by moving the car back), or easing the jib before the main, that way I don't run the risk of closing off the slot. My general system for depowering from initially having both sails set for max power is: 1st both sailors trapped out, then downhaul until maxed, then travel out the jib slightly (or ease sheet if no jib traveler). Ease main traveler.

One last note, if the boat feels sluggish, it's usually a good idea to ease the jib slightly. An oversheeted or stalled jib is very slow.

sm