Most often I've seen it in the form of jokes. You're in the final stretches of negotiating a deal with someone you consider a friend and they make some joke about how now they're going to stop showing up to work. Red flag. You might think "why would someone say something like that?" I was negotiating a deal where the other party was guaranteed 7.5MM over the next 5 years. They made the joke because they thought they already had me wrapped up in the deal. I walked away based on that joke alone. The logic is that at some level they're trying to prepare you for what you're in for. Everyone's armor has chinks. As the deal gets closer to being done you see the real person on the other side of the table.

Another red flag is if you put something in email and they call you to respond on the phone. I treat email almost entirely defensively now. It's simply a record of things I'm comfortable being read aloud in court and a memorialization of what was agreed to in conversation. If I'm not comfortable with it being read in court it's discussed on the phone or in person.