Adjusting the pivot on a folding knife
On many modern folding knives (like those produced by Benchmade, Zero Tolerance, Kershaw and others) you'll find an adjustable pivot. You can loosen or tighten the pivot screw, setting the knife's action to your liking.
The goal is to find the "sweet spot." Exactly where that is will depend on your personal preferences, and there's a trick to getting it just right.
Using the proper tool (usually a Torx driver, like those supplied with Benchmade's BlueBox Tool Kit), make a slight adjustment in the direction you think you want to go (looser or tighter) and live with it like that for a little while. Then, if you need to, fine-tune the tension of the pivot until it suits your fancy.
Of course, you don't want the pivot so loose that the blade flops open in your pocket. Then again, over-tightening the pivot can make the knife essentially unusable and cause premature wear.
Adjusting the pivot of a new folding knife
A folding knife, like most mechanical devices, has a natural break-in period. Its contact surfaces take time to "mate" -- regular opening and closing of the blade will "polish" the surfaces. During break-in, you may want to resist the urge to adjust the pivot.
A brand-new folder might seem tighter than you'd like, but it probably just needs some use to operate smoothly. You shouldn't try loosening the pivot screw to "fix" a problem that doesn't exist, and besides, you'd only be postponing normal break-in.
Give your new folding knife time to break-in naturally before fussing with the pivot. It'll be worth the wait in the long run.