Apart from casual work on building sites during vacations as a student many years ago, I've no "vocational" training or experience for anything likely to come up here.
But over the years I've tackled some quite substantial jobs on various properties with the help of my father, who was a master bricklayer until he retired some 30 years ago. Him the brains, and me the brawn, I'm afraid - though I did eventually learn to measure twice, cut once.
And since I'm in the UK, where we have 240V mains, I always check electrical wiring with a neon mains tester screwdriver. Before turning anything off, to make sure the tester works - and after, to make sure the power really is off.