Avoid craters by not picking at them. Skin has elastic properties so bumps and spots, while unsightly, won't usually leave a scar *unless* you've turned them into open sores by picking at them.
If you have a yellow/white spot with obvious pus just below the surface that you really can't leave alone, use a fine needle to lance it and carefully ease the pus out with gentle pressure rather than "popping" them. Immediately treat the area with astringent.
However, this is best for "standalone" spots. If you have clusters of them in close proximity, or if the area is angry and inflamed, you may make things worse for the neighbouring acne. Frustrating though it is, the best course of action is facewash and patience as Virginia Marie described.
Oh yes, one final note - you may have seen those little implements with a fine wire loop for removing whiteheads and blackheads etc.. They work better than fingers when easing out pus because they help apply the required pressure in a more controlled way.
Bottom line, never pop acne open by finger force.
