x2 on the star drive deck screws. That's all I buy these days. Three inch screws for standard (1.5 inch thick) lumber.
I tend to go overkill on my decks. On corners, I bolt twice to posts, 90 degrees apart, using 5/8 inch by 8" or 10" galvanized machine bolts with washers and square nuts. These bolts can be bought at utility suppliers; they are used as pole line hardware. I have jacked and repaired decks where the original builder used deck screws in shear to fasten the stringers to the posts, and the screws sheared off. Never use deck screws where subject to heavy shear, especially with live loads.
