Values that actually show up in decisions
Posters on the wall don't work. Values written into how you hire, fire, and praise do.
Three to five values, in plain language
Not corporate words. The phrases you actually use ('show up early', 'do the right thing when no one's watching', 'leave the truck cleaner than you found it'). That's a values list.
Hire and fire on them
If a value never affects a hire or a fire, it's decoration. Owners who actually use the list see the culture follow.
Praise the behavior, name the value
'Hey, the way you handled that customer is exactly what we mean by [value].' That's how a poster turns into a culture.
Take your version of this question further
This is one operator-tested angle on the question. Your shop, your size, your trade, and your team change the answer. Ask your specific version inside Ask a Shop Owner to get a response grounded in how owners like you actually handled it.