In the photo above, many users think that turning the seat around is the only way to signal to people that the bike is broken. They clearly have no idea that they can push a little button on the kiosk and the light will go red locking the bike until a repair van arrives.
The other common mistake made involves the Citi Bike seats. The lever that tightens the post can be clamped down far too tightly if the little twist screw is turned clockwise. A common scene is a banker-type person struggling mightily to get the lever to snap shut. All they need to do is untwist the screw.