Smooth the result, and you have an excellent base for creating a round Phillips screw head.  The rest is pretty elementary modeling in my opinion; just create some support loops along the cross edges, and create a bottom to the head, then subdivide once or twice (depending on your resolution needs).  The result should be a nice round screw head, with cross insert, all quads.

Like I said, I think the rest of the model is pretty simple after this point, but if you want me to continue with more examples, or get stuck on any step, just let me know.

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