Electric Relay Advice

Hey FABO electrical gurus, I'm looking for some guidance on relays. Specifically, what to use them for.

As I'm getting closer to finishing the wiring on my 70 Duster, I'm thinking about relays. But, I don't really know where to use them.

At this point, I know I'll use relays for the headlights and electric radiator fans, but I'm wondering about some of the other modifications that I've made.

So, would you recommend relays for the following...
- electric trunk release
- aftermarket stereo system
- push button start
- aftermarket A/C
- back up camera

Are there any other components that would benefit from having a relay installed?

Thanks for any replies