... obey private speed limit signs, especially if they are not divisible by 5 or 10.
... wear shoes while driving. It is an urban legend that it is illegal to drive barefoot.
... write your account number on checks that you mail. What a pain. I did this for a year or 2, haven't in decades.
I change my oil every 7000 or so miles. The rental car companies use 6500. My RAV4 has 225,000+ miles, still running fine (routine repairs only).
Regarding speed gun calibration (and the poster who said the cop would laugh), the cop doesn't matter (duh). You bring this issue up in court. It works fairly often.
I have heard the same warning about driving in neutral that was brought up.