Be firm. Not a pushover, and not an asshole, just solidly in between. "Tough, but fair" is what I was taught.

It also helps if you know a bit about all aspects of the trades, so you can call guys out on either bad work or bullshit excuses. "Oh, I had to do this because..." No, it was just easier to do it this way.

It helps tremendously to review at the start exactly what your customers want. You can even blame it on them. "The contract says this and this and this, and I know the owners are particular so we need to make sure we do X". Even if the customers didn't say anything about it.

Gotta know how to phrase everything too. "Hey, the customers were really impressed when I showed them a picture of our last job, so they're looking for a really good job like that here." Even if that's not entirely true either.

Yeah, you'll run into some shitbirds but for the most part just treat everyone with respect, but make your expectations clear.

Sometimes you have to flip on the asshole switch, but that shouldn't be the default setting. We had a plumber run a drain line right down the middle of a finished basement ceiling. I told him he had to move it and he just said, "Too bad."

"Yeah," I said, "it is too fucking bad, since you're about to take this down and do it right. Tell your boss to call me if that's a problem."

But if I'd said nothing, the owner would've complained and I'd be dealing with that, and still have to call the plumber back to move it.

And I've only kicked one person off a job. A story for another day, but that's the only time I ever thought I might get into a fistfight on the job.