[Xearo]

hah i had a whole thread just about that!!
The deck: There is a cross support behind it for the center console. There was a small screw that didnt hold anything on. I assumed it was a for a ground, so I just ran a grount wire to it. Works well.
Amps: Each amp is mounted beneat the seat. The little cutouts in the carpet where the cables come out of, I just drilled a pilot hole, scraped of the paint and put a washer over a wood screw. Just kid of carefully drill in the woood screw with the ground wire wrapped around it. Did it for both amps. Works well.
Hideaway unit. The cross member behind the rear seat, same thing. Drilled a pilt hole, scraped all the paint off around it (used a dremel) and same thing wrapped the ocnductor of the ground ccable around the screw and carefully screwed it in. Again with a washer to helppush the coinductor against the now bare metal for good conduction.