So true. Another good point is to ask to use the restrooms even if you don't really have to go.
I interviewed at one place where I was told over and over how well the company was doing and how the owner loved racing his Porsches at the local road track. Then I saw the restrooms, which looked like they hadn't been updated or fixed in twenty years. I figured out where the money was going... and it wasn't to employees.
Sure enough, the offer came in and it was a lowball. That confirmed my theory.