You can ground them to any spot of bare metal. For my LED doorhandles, I have it grounded to the metal frame around the fuse box.
As for my power, I used a vampire tap in line with the switch that powers my headlights/instrument cluster.
I have a secondary switch that I installed in my center console so that they can be turned on/off independant of the headlights.
If it wasn't for law enforcement & physics, I'd be unstoppable.