Multihull girl is right. Lifts lift you towards your destination when beating upwind but may be less welcome downwind since it could turn a broad reach (usually faster) into a dead run (slower). Headers opposite.
Another thing is what kind of wind/weather is it? If it's a "persistent" shift in one direction, then you want to get there first and be to windward of the competition and stay there so you sail less distance than they. Lifts help the windward boat and hurt the leeward boat. And again, headers opposite.
But if it's an oscillating wind, back and forth every few minutes (more common after a cold front passes, at least where I grew up), then just figure out the "average" wind by taking a few shots into the wind and watch your compass, or go close-hauled on both tacks and watch your compass. That way you'll know if you're heading worse than "average" at any given moment, or better. If better, stay on til you get headed, then tack. If worse, tack away and it will (should) be better than average on the new tack.
"Tack on headers--stay on lifts" is good "vanilla" advice. "Pistachio fudge ripple" exceptions to this, in particular situations (usually at the beginning or end of a beat) can be learned as you go along.
It's why racing, especially upwind, is seldom dull.