When drilling a pilot hole for a #8 standard wood screw in hardwoods, one should use an 11/64-inch tapered drill bit. A 5/32-inch bit should be used for drilling into softwoods.
When using square drive screws, a standard point drill bit should be used. Hardwoods require a 1/8-inch bit with softwoods needing a 7/64-inch bit. Both standard and square drive screw plugs should be pre-drilled with a 3/8-inch drill bit. The bit used can be either standard point or tapered. The screw size number generally indicates the diameter of the screw; the higher the number, the larger the screw's diameter.