I wouldn’t dare defile Douglas Adam’s memory by not mentioning that you should keep a towel with you at all times, but my second contender is a surprisingly short three-parter:
- never lie.
- never tell the whole truth.
- never pass up a chance to use a real bathroom.
Even in court you have to use some judgment to determine what the whole truth is, under what context, and to the extend of your memory or a reasonable expectation of enforcement of the idea.
There’s also limitation with self incrimination/5th.
But as a generality, omitting information on socials, whatever registration form, etc… In everyday life is a reasonable practice for preserving privacy.
Being dishonest with friends & family is messed up tho.