This means that you need to vary tension not only when the breeze changes velocity, but when you change point of sail.  Since there is more apparent wind when you sail upwind you will need more tension than when sailing off the wind.

Hoist sail with minimum (hand tight) halyard tension.  Sheet the sail appropriately for the point of sail (see section on sheet tension).  With the sail now loaded, tension halyard just enough to remove any horizontal wrinkles emanating from the luff.  (Wrinkles will be at right angles to the luff).  In light apparent wind velocity you can leave just a hint of wrinkles.  As velocity increases, wrinkles will reappear and additional halyard tension will be needed.  Avoid over-tensioning.  A vertical wrinkle or “gutter” parallel to the luff is a sign of too much halyard tension.

Ease the sheet and boom vang when adding halyard tension.  There is no point in fighting a fully loaded sail.

If you are trimming a racing mainsail, do not raise the head of the sail over the black band at the top of the mast, which delineates maximum legal hoist. If more luff tension is needed, use the cunningham to pull down and remove horizontal wrinkles.  The halyard and cunningham do the same thing–provide luff tension–they just work from opposite directions.

If your mast is capable of bending, more bend will require more luff tension and vice versa.  Add halyard or cunningham when adding mastbend, ease tension when straightening the mast.