What are your personal guidelines on lending money to people you know?

I know people always say “don’t lend an amount you can’t afford to lose” because when lending money, it’s possible you’ll never get the money back.

If people ask you to borrow money, what are your personal guidelines (if you have any or can think of any) and criteria for lending money to them? What amount, what you expect as far as when you get it back, if payments are acceptable instead of the whole thing at once, etc.

I’m not asking for any particular reason, just curiosity.