when controlling the gib, should i use the windward or leeward sheet?
Prior to tacking, the leeward jib
sheet will be taut. When tacking, after the helmsman puts the tiller over, the boat will begin to turn into the wind. The jib will begin to luff and then flap. At this point the leeward sheet is released and the windward sheet will be taken in. At this point the boat will be on the new tack and the formerly windward sheet will be come the leeward sheet and will be taut. Do not release the jib before putting the helm over or the boat will stall.
For example, in my avatar, we are on a port tack and the starboard (leeward) jib sheet is tensioned. When we tack to port, we will release the starboard sheet and take up on the port sheet, but only after the boat has passed through the eye of the wind. Prior to tacking, I will call "Ready About". When the crew responds (particularly the two jib sheet trimmers), I will call "Tacking" and then put the helm over gently to allow a controlled maneuver and allow the crew time to release the jib sheet and take up on the lazy sheet. Sail trim always adapts to boat course, not the other way around (unless you're a lazy cruising slug and don't want to put down your beer and get up to trim the sails
There are some refinements that I left out but this is the basic idea.