I have been in a few times (psych ward) and I 2nd what @jatty said so eloquently, keep one's mouth shut and answer as few questions as possible.
Case in point, one time when i was in, I said something stupid like "just wait till I get out, goodbye!" , well 1) my stay was extended 2) almost everyone in the ward could leave and go to Sunday Services on a different floor, BUT me, oh no, we do NOT trust you after what you have been saying.
Lots of books, puzzles and the like, keep your head down, and say nothing.
Walter