not using the brake
In terms of performance, one of the most important lessons is that the rudder functions as a brake; the more you must rely on the rudder to get where you're going, the slower you'll get there. The sails are balanced at the point when the boat sails a desired course with the rudder amidships. This is not simply a matter of balancing the center of effort between jib and main. On smaller boats, sail balance can sometimes be achieved by shifting crew weight. On larger boats, sail balance is sometimes a matter of the finer points of sail trim, such as keeping an open leech on the main, or changing the amount of twist on one sail or the other. For example, my 410 often develops lee helm in light air. I solve this imbalance by easing the jib an inch, moving the main traveler to weather while sheeting out (thus introducing twist) and by asking the crew to sit a bit forward on the leeward rail. I can suddenly sail close-hauled with the rudder amidships, which tells me I'm balanced.