[DonC]

Conventional wisdom seems to be to snug them down firmly and then give it a couple of shots with the hammer.
You might want to keep in mind that you want to have the car on the ground before applying the hammer to the spinners to help save the wheel bearings.
I have to respectfully disagree with Bob about leaving slack in the wire. My advice is to keep the wire tight. It will help prevent the spinner from starting to back off if it is going to and if the wire breaks you know you've got issues. I come from an aviation background where safety wire is a way of life and it's never left slack.
As always, don't forget the anti-seize. I've got stainless spinners and still use it even if I don't have to worry about like metal galling.
DonC