Experience. Start with the simplest of things: replacing a standard (non-GFCI) receptacle. Buy a book that tells you how, or learn from someone who knows. (Both is best.)

Don't guess at anything. If the book doesn't say exactly what to do in the situation you're in, hire an electrician. (This sounds overly cautious but really – if you're doing something even slightly "novel" then there's either going to be code issues you aren't qualified to judge, or actual electrical issues you aren't familiar with and don't even know to think about, like grounding issues.) Thankfully, most situations a homeowner will encounter aren't left up to interpretation by code, and are therefore covered in a good book.

Move on to similar things (say, replacing a simple switch or GFCI receptacle) when you feel you have enough experience.

When I was young (< 14yo) I bought a book at Lowe's called "The Complete Guide to Home Wiring". Of course, this was abnormal but I had an extreme curiosity about electricity. (I still do which is why I'm an EE now)

Here (Norway) it's whenever it involves the work on the mains panel or on unterminated power wire. You can change ceiling fixture if it has a clip in power socket, you can of course change lightbulbs (doubt it's licensed anywhere in the world), you can even install electric flooring that clicks to connect. You can't do anything that requires tying or soldering power wire together, and you can't install hidden cabling/channels and fixtures yourself (fire safety reasons).

I find that hard to believe. In the US you can't market yourself as an electrician/handyman unless you are licensed.

But you can fix you or your neighbors outlets all you want.

The distinction is drawn at being a business vs yourself. But, we still have that individualist spirit, so I could be wrong about other places.

In some cities you would need a permit to replace an outlet. And only licensed electricians are allowed to get permits. In some cities bad wiring jobs don’t just burn you own house down, it’ll take the neighbors house with it. So it’s not just your butt on the line if you screw up.

People do that anyway, just that you'll have tough luck if it comes up in an insurance case. Or worse if you are in a condo and other people suffer.

Wiring and outlets are simple enough, but you wouldn't believe peoples' capacity to botch things up. They'd connect a ground pin socket in place of non grounded one without changing the wiring, or use incorrect section wire, or with incorrect insulation type for in-wall application, or they'd replace a charred outlet without trimming the sooted part of wire. Enough nuances to avoid amateur work.

So can you change an electric outlet? That means turning off the individual circuit (or mains if you are paranoid) then opening, disconnecting, connecting a new one.

What about installing a ceiling fan? Assuming the wiring is already there.

No you can't change an outlet yourself, legally. And ceiling fans are really uncommon in Norway.

But am sure plenty of people do small fixes anyway.

Does that include running Ethernet or HDMI and other low power cables?

You can put exterior signal cables yourself. The wall conducts for such cables still have to be put in place by electricians I believe, but not 100% sure.

Most likely you can freely do the installation yourself but it has to be connected or maybe just cross-checked and then signed off by a certified electrician to become a legal installation. That's what homeowners commonly do to save money.

Even for cat5/6 installs ?

That cat5 cable seems like a safe enough thing but it’ll wreck your day if it shorts something else carrying more juice.

You don't need wall conduits for low voltage cables. The 'boxes' for them are just meant to hold a cover in front.

Modern safety features shut it down if current goes into the earth, so the most dangerous is if you touch both wires and are well isolated from the earth. This makes you look like a light bulb to the safety features. The other danger is that it sets your house on fire a week after you've "fixed" something.

That said, as a kid I played with 230v electrolysis (stupid I know) because my 30v version was too slow. This is basically the worst case scenario: electrodes close to each other + water + combustible gas + potential for sparks + deadly voltage, but the safety system shut the power down immediately when something went wrong.

> Modern safety features shut it down if current goes into the earth

What? No, that's only true for GFCI circuits, which are not the norm in the US (typically only found in bathrooms and kitchens, though the NEC has been slowly expanding the requirements). Touching hot can kill you and the breaker box won't care.

Actual safety advice:

1. Buy a current sensor. They're like $5 from Home Depot (speaking of).

2. Turn off the breaker, and make sure it's the right one by using the current sensor.

3. If you're in a situation where you cannot turn off the breaker, wear rubber-soled shoes, and work with one hand and place the other behind your back. (This prevents current from traversing your chest cavity.)

4. Buy a receptacle tester (again, $5) and use it to test your work.

5. If any of the above is not obvious to you, hire an electrician.

And, like red, green refactor, make sure the current sensor correctly detects current before you turn off the breaker. Then make sure it detects no current after you turn off the breaker.

Oh, where I live they were made mandatory something like 50 years ago so I assumed they were standard in every developed country because they cost $30 a piece so why not? Much better life extension value for money than a medical checkup. I wouldn't want to live in a house where every appliance is a potential death trap. They might even pay for themselves purely in cash if they save you an appliance. Mine activated just last week when someone dropped water over the power extender contact and still proceeded to turn it on.

Ya the US is somewhat behind other countries electrical-safety wise. Another weird thing – all our receptacles are flush, not recessed, so the prongs are still exposed after they've made contact, when the plug is halfway in.

This is compounded by the problem that Home Depot still sells, e.g., non-tamper-resistant receptacles. They are no longer code compliant, but they're by far the cheapest and I've no doubt they end up in the homes of tons of DIYers.

I get a permit for my work, and the inspector comes to verify that I do it right. I sometimes make small mistakes, but the inspector gets me to correct them before something goes wrong.

I have also read several books; watched several videos; and watched other people do this work. Over time I've picked up a number of things, and the different sources helps ensure I can pick up on what is correct vs what looks like it works but is wrong.