1) Buy the NEC code. It ranks somewhere between Shakespeare and Greek Mythology on my "enjoyment of reading" scale, but has a lot of necessary info. I had to read several sections multiple times and do some research to understand how to interpret the code. And I'm an engineer with some electronics in my background.
2) If you know anything about firearm safety, the first thing to do if you pick one up (excluding a few select circumstances) is to make sure it is clear, or unloaded, before you do ANYTHING else.
Well for electrical safety, before you do ANY work, use your voltmeter, test light, or whatever on EVERY wire you may touch during your work to make sure that none have voltage, ie they're not loaded. Never assume anything about a wire based on it's insulation color, or anything else for that manner. Always test. Ignorant people wire stuff in all sorts of incorrect, illogical, unpredictable ways.
3) Inspectors are sometimes quite helpful, and it can be good to have a good relationship with them. They can also be quite a hindrance at times even if you are doing things according to their rules. YMMV.
4) Don't go overdoing things and making everything 12 gauge wire even if it doesn't need to be. I did some of that when I first started b/c at the time I was too cheap to buy another whole roll of 14. 14 is a bit easier to work with, and is cheaper to boot. I now keep both around.
5) Never accept advice from people on the internet

Sorry, had to throw that one in there. This advice is worth everything you paid for it
