Through the years I have identified recurring rules that underly most of my "bugs", "failures", "mishaps" and other blunders.
Rule 1 : If you connect it to the power supply, it works better.
Rule 2 If you connect it with the right polarity, it works even better.
You could argue "it goes without saying" but it goes better when you say it ;-)
Please comment and contribute with your own "golden rules" :-D