Please feel free to add your own...
Power supply testers are $10-$15. I highly recommend getting one and use it for troubleshooting. It's a lot easier than shuffling cards and cables around and it will save you time if you ever have to troubleshoot power problems.
Correct, a tester would be the best thing for power troubleshooting rather than on shuffling things up because of your presumptions and guesses.
If you have to sell your mined coins immediately to pay the electric bill, you probably dont need to be mining (have some working capital)
I do completely agree on this line where you should not rely on your mining earnings on paying up your bill because you might be fucked up when you do saw your outcome is too low to pay the expense.