Considering the amount of time I spent as an undergraduate designing analog circuitry, I thought I'd be a decent electrician.
This couldn't be more wrong.
1. My dexterity skill is low, maybe a 9. I'm a klutz, have poor motor skills, my hand writing is illegible, the list goes on. This does not work well for wire manipulation. Actually this does not work well for manual labor in general.
2. Theoretical knowledge of electricity doesn't help much; it may even hinder you (it hinders me). In general, I like to explain everything, my husband calls this phenomena, Wendy's wack a** theories. I think coming up with connections and reasoning (more like randoming) is a lot of fun. With electricity, my theories are convoluted, usually involve Ohm's law, and are ALWAYS wrong.
3. I lack patience and after failing at wiring a circuit I start hacking away at it, just trying to make anything work... Constantly running back and forth to and from the circuit breaker. Like hacking code, this just wastes time and leads to poor quality. Not the best sacrifice when it comes to electricity in your home.
Recently, I've spent a great many hours changing a light fixture, outlets and switches around the house recently and I've come away with this knowledge:
1. A voltage tester is a worthwhile investment. I don't own one, but I really, really should. Its like coding without a debugger and with no TDD, a debugger would be quite useful.
2. Before you replace existing circuitry, study the current setup carefully before taking it apart. Otherwise, you will be confused by the 8 wires available when you only need 2.
3. Like working with other peoples code, working with others peoples circuits is scary, and things built a long time ago were built, well, oddly. Keep this in mind.
4. Refactor existing circuitry one switch, outlet, etc at a time. Its annoying, because you need to return to the circuit breaker a lot (unless you live on the edge), but at least you are always in a working state and you know when you broke your circuit.
5. If you are replacing an outlet with two pairs of wires, it is either powered by separate circuits or powering something else. You can check the hot side of the circuit to see if the bridge connecting the top and bottom is there -- if it is, then the bottom wires are being powered by this outlet, and you don't need to remove the bridge on the new outlet. If its not, remove the bridge on the new outlet. If you get this wrong, things will break.
6. Having a pair working with you is priceless. They can call 911 for you. And I was told this afternoon that your dog doesn't count (unless it knew how to call for help).
7. No matter how annoyed and frustrated you are, its never a good idea to do one more quick "test" without turning off power at the circuit breaker.
If I approached circuitry like I approached software, I would be a much better electrician! I suspect applying agile and xp methodologies work very well for all home improvements. I hope I remember this tomorrow morning!