For especially sails made of 'dacron' and NOT rolled-up on 'furlers' .......
The simple answer (for when closehauled), usually ignored by almost all cruisers, is
1. change the mainsail halyard (and/or cunningham) tension ... which repositions the where the 'position of maximum draft' occurs in the mainsail - to rebalance the helm pressure. The more 'fore' where the max. draft occurs, the lesser amount of so-called 'weather helm' (if the boat was set up 'correctly' in the first place).
2. be sure that the headstay is not 'sagging off to leeward' which promotes a boat to 'skid to leeward'.
Several easy steps to determine exactly what is going on when you 'develop' so-called weather helm when attempting to sail 'close hauled':
FIRST is to look at the stern wake ... see if the rudder and keel turbulence wake is coming almost STRAIGHT off the stern; if not, then youre probably skidding and you need to tighten the forestay (via backstay tension).
SECOND, If the stern wake is seemingy 'straight', then you probably have 'weather helm' and you then need to change (usually) to more halyard/cunningham tension until that so-called weather helm is lessened or eliminated. (If you have a 'rudder position indicator' if the 'gage' is showing more than about 4-5° of rudder angle to hold a straight course when 'beating' ... thats 'weather helm', usually easily corrected by (more) mainsail halyard tension). You simply cant do this with sails on 'furlers'.
BTW#2 if youre dragging your rudder almost sideways to correct for 'weather helm', that will result in a slower boat at greater heel angle ... and that greater amount of heeling will also contribute to 'weather helm' in some (non-symmetric hull shape) boats.
Rx: With a boat that was previously set up with 'proper' rigging tension, when you develop 'weather helm', the FIRST thing to do is look at the stern turbulence wake to determine if: 1. boat skidding off to leeward (too loose forestay/backstay); or if, ....
2. actual weather helm (too loose main halyard/cunningham tension).
.... and every damn day requires different tensions depending on wind speed and wave height.
• Mainsail luff (halyard) tension - How to properly RAISE a woven dacron mainsail - SailboatOwners.com
• Forestay (backstay) tension: http://www.ftp.tognews.com/GoogleFil...f%20Hollow.pdf