Predrilling

Predrilling (drilling a pilot hole before driving a screw) gives the screw a path to follow that's narrower than its threads but doesn't require the wood fibers themselves to split apart to make room. Skipping it, especially near the end of a board or in a species prone to splitting, is one of the most common ways a screw cracks the very piece it's meant to hold together.

Beyond preventing splits, a predrilled hole also keeps the screw running straight and centered -- a screw driven into solid, undrilled wood tends to wander slightly off the intended line as it fights its way through, especially in harder or more figured material, where a pilot hole gives it a clear path to follow instead.