Shouldn't need saying, but

ALL GUNS ARE ALWAYS LOADED. You can't trust the SOB in front of you in the Fun Show.

ALL WIRES ARE ALWAYS HOT, and it doesn't matter who signed the lockout/tagout card. That's why God gave you a VOM.

THERE'S STILL WATER PRESSURE even though you shut it off at the mains, and the minute you disconnect the toilet supply line you'll get all the water from upstairs. This applies especially to blackwater lines.

YOUR MIDDLE NAME IS MURPHY and the law follows you wherever you go

Oh, and the jackhammer doesn't know you big toe from the pea gravel, and that’s why I wear steel toed sandals. And you probably can't bench press your car, so use the damn jack stands. If you say “Hold my beer and watch this” it's probably a bad idea. If you're doing something to post on YouTube, ditto. Likewise anything starting with “Bet you can't”, or “So we started drinking Tequila”.

Damn , that's a good line, I'll have to remember it. “Your Middle Name Is Murphy” and don't you forget it.