Originally Posted by Jayhovah

One of the best things I've done, as I find myself hardwiring plenty of accessories (radar detector, laser jammers, backup camera, steering wheel remote adapter, homelink mirror, gauges) was to add dedicated circuits and wire in some terminals for constant 12V and switched 12V. Makes it a ton easier every time I want to add something new, and keeps me from having to constantly tap the OEM harness.

I used terminal block similar to these (and just wired one side all together so one block would be all +12V or switched 12V):
https://www.amazon.com/Position-Term...terminal+block

And I added the circuits with things like this (you need one of the mini versions per circuit, so two if adding both a constant and switched):
https://www.amazon.com/Moeye-circuit...uit+mini&psc=1


MUCH better terminal block for this type of use (just more expensive):
https://www.amazon.com/Busbars-Point...ribution+block