Most boats perform best upwind with a nearly neutral weather helm. At times, the boat will develop weather helm, especially when in point mode, but an excessive tug on the tiller indicates that the boat is badly out of balance. The quick fixes: sail the boat flatter, raise the centerboard, decrease mast rake or flatten the mainsail.
In most conditions, trim the mainsheet so that the top batten is parallel to the boom, rather than pointing inboard or outboard. To judge this, cover the last 10 inches of the upper batten pocket with black tape. Then sight up the leech from under the boom, trim to the right spot and mark the mainsheet.
That said, there are times you can break this rule. When trying to accelerate, develop power in light-to-medium winds or when greatly overpowered in a breeze, the upper batten can be angled outboard 10 to 20 degrees.
Conversely, when trying to point extra high in moderate air, it's OK to slightly overtrim the main so that the batten hooks to windward in relation to the boom.
Figure out what is maximum mast bend, and then strive to attain it in most conditions. Maximum bend is the point at which overbend wrinkles (speed wrinkles, inversion wrinkles, etc.) develop in the lower quarter to lower third of the mainsail. Depending on the boat, you can bend the mast with mainsheet tension, vang tension, backstay tension, rig tension, mast blocks, spreader angle or a combination of all of the above.
Every boat has its optimal rig tension. Find out what it is and maintain it. Most boats sail best with the rig just tight enough so that the leeward shroud starts to go slack when it's blowing 10 to 12 knots.
If the rig is too loose, the jib entry will become quite full. The result is poor pointing ability. Too tight a rig, on the other hand, is sometimes indicated by overbend/inversion wrinkles in the entry of the jib — a small scale version of what happens to a mainsail with maximum mast bend. In addition, if the rig is too tight, the entry of the jib will be quite flat and the telltales will break on both sides of the jib at nearly the same time. In short, the jib becomes hard to steer to.
Sail the boat on its lines. Usually, a boat will not perform when its bow or stern is buried in the water. Besides the obvious drag, this can affect the balance of the boat and the tug on the tiller (e.g. bow down creates weather helm). Instead, position the crew weight so the transom is just kissing the water. The result is a smooth, undisturbed wake. Watch where the top sailors sit and copy them.