I was thinking about some of those random handy things I'd picked up from people.
Here's a few...
Avoid cross-threading things: turn whatever it is in the 'loosten' direction until it goes 'thunk', then tighten (father)
For general storage, old hard-plastic instant
coffee jar lids fit NZ preserving jars (mother)
Sharpen most blades on a really acute angle (chef boss)
Don't wash bread tins, and dry baking tins in the still-warm
oven (nana)
House music is an instrument of the devil (a wise friend

)
What small, but really useful things have you learned, and who taught you?