Wiring 101 Question - Switch / Relay Power

Hey all - so, I'm trying to educate myself on the basics of wiring up accessories. I understand the basic concepts of fuses, relays and switches. One question, that I wanted to get some feedback on, is in relation to tapping a power source for the switch. I often see/read recommendations to tap into an existing wire to power the switch. But, because the power draw is negligible, it doesn't really matter what you tap into for the switch, assuming it has power when you want it. I'm sure this works just fine when dealing with things on a one-by-one basis, but I'm thinking that as the list of accessories you want to power grows, this is an area that can become a confusing rat's nest of wires.
So, that's where I'm trying to understand what's the "best" or "cleanest" way to tap into a power source that you connect the accessory switch to? For instance, is it ok to tap into the main power line that is going to power the accessory itself (before the relay) and send that to the switch, which will then also connect to the relay? My understanding is that the connection between the switch and relay will draw very little amperage, so i should be able to tap into the larger gauge main power wire before the relay and send that to the switch. I'd like to be consistent in how I approach every wiring project on my truck, which I think ultimately lends towards a "clean" install.

I have a Painless auxiliary fuse block that I'm looking to mount in the engine bay. It has 3 always hot and 4 ignition hot fuse locations. Would it be "cleanest" to also put 7 relays mounted somewhere near the aux fuse block with main power going from each fuse location to each relay? Then, tap each one of those main power wires before the relay and send each of those to a switch, which will also have a wire that goes back to the relay to complete the circuit. So, i think for each switch in the cab, I'd have 2 wires coming from the engine bay (maybe a third depending on where i ground?). The other main power wire that is the output of each relay would then go to the accessory itself.

Does this sound like a standard way of approaching wiring up accessories?

 

So that got a little confusing, but from what I gathered it sounds like to avoid excess wiring, you want to run a hot from before your relay into the cab to your switch, and then back out of the cab to the relay. I think the reason it is said as tapping an aux wire is because you can pick up a hot inside the cab, and one run out of the cab. just one direction not doubling back. Otherwise I don't see anything wrong with your plan, although I am no expert, i'm just about to start my light wiring project myself.

 

honestly everyone will have a different opinion on this topic. to me, less wires through the firewall the better. ultimately you need to plan ahead on this. much easier to run all the wires once.

lets start with this question and we can go from there.

the fuse block, what will you be powering off of it? where will the end items be? in the cab? in the engine compartment?

there is a million ways to skin this cat... but we got to start somewhere.