You need to learn how to break problems down and rule out possiblities. You don't start into a problem with a theory that immediately requires massive disassembly or intervention.
Very concise description of the best approach to troubleshooting.
To it I would add that it is essential for effective troubleshooting to really understand how the piece of equipment in question works. Not just "how to turn it on" but how it's functioning inside. Because if you really understand how it and its components function you can do a huge amount--- if not all of--- the troubleshooting in your mind. And then zero in on the few or maybe only one thing that could be causing the problem.
On a particularly frustrating day having to do with toilets not long after acquiring our old boat I bellyached to the GB broker who found the boat for us that I was getting tired of dealing with stuff and wished I could just pay someone to do everything. He said that while that can be nice, the downside is that he sees lots of wealthy owners with beautiful late-model boats who haven't got a clue how anything on the boat works. And sometimes you can't spend your way out of trouble, as when something important fails mid-cruise miles or days from a mechanic. Working on the boat's systems yourself, he said, teaches you how it all works, which means you learn what can go wrong, which means you learn how to diagnose and fix it.
And he was absolutely correct. It doesn't make working on toilets any more fun but it removes the worry and frustration and "why is it doing this?" fear.
We currently have a very bizzare issue with our fresh water pump. While I don't know how the pump innards specifically work, I am 99.999 percent sure I know where the problem is because I understand the boat's fresh water plumbing system. And after analyzing what's going on and eliminating every other cause, to paraphrase Arthur Conan Doyle I have eliminated all the other possibiilties so the remaining one, regardless of how improbable it seems, must be the solution to the mystery. And I didn't have to tear the boat apart to get to this point.
When I fly a plane I don't bank the plane by turning the yoke. I know how the wing works and what it needs to do to the air in order to bank the plane and thus change the direction the plane is flying. I visualize what I want the air to do around the wing to make it bank. And in order to make the air do what I want it to do to bank the wing, I have to turn the yoke.
There is a difference between the first sentence in the last paragraph and the last one. Subtle, perhaps, but it's the difference between simply doing something because you think or were taught that that's what you're supposed to do, and doing somehting as a result of understanding the "system" well enough to know the exact action it will take to achieve the desired result. I believe that same philosophy should be applied to troubleshooting.