What type of screws do I use to fasten vinyl siding?

A standard #6 x 1 ½” to 1 ¾” coarse thread “bugle” style or “flute” head (1/4” dia. head) zinc coated or otherwise non-corrosive screw will do nicely (NOTE: as inexpensive as they are - drywall screws with the black sulphur coating will eventually corrode).

Equally as useful are standard bright (chrome like) finish #6 or # dia. x 1 12” pan head coarse thread self-tapping screws. These have the added bonus of being able to be used for a multitude of anchorage purposes besides siding fastening and do not corrode as easily as drywall screws.