One thing that really burns my biscuits is Circumstantial Exposition. This is my name for when a sloppy writer wants his characters to act in a way that makes absolutely no sense, and they just drop in an explanation right along with the offending behavior.

For example:

And then, Billy decided to get into the car with the stranger. Did I mention that Billy was extremely trustful of strangers? Well he is. Cause he was raised in an orphanage in Ecuador where he lived with deaf mute monks. Since he couldn't speak with them, they were like strangers.