Also check Mast
Julius: Weather helm on my 1975 C22 is usually overcome by setting the shrouds and forestay properly during the setup stage, so that the top is about 6 in. aft while bestilled in calm water (determined by putting a weight like a wrench on the main halyard before putting on the boom). In strong wind I can also bend the mast aft a bit with an adjustable back stay. The result is to move the wind forces aft which removes weather helm. But you can overdue this so that instead of slightly rounding up when you remove your hand, rather you round down which could get one into a little trouble I suppose. Best to set it up so that there is just a little rounding up on the helm while tacking. Balancing the main against the jib as others mention is also important. I was taught to set the jib on a tack just right so it is full and nicely curved but close to losing the wind (telltales streaming back parallel to water), then to set the main in a very similar position so that their curves are similar and the slot between open. From there you can adjust just a little for helm pressure. Dick K.
