How do I connect a new Lutron sensing switch?
I think I've installed the switch you are talking about before.


Blue wire (traveler) is for 3-way applications, just cap it off
Green wire (ground) ties in to the exposed copper wire of your Romex, or into the box if you have BX cable
Black wires: because you are using AC current, the switch doesn't really care which side of the circuit is truly 'hot'.  You just need to tie in one of them to a hot wire (A), and the other to the light(C).