These may take quite a bit of thought. This should get the player thinking in the mode of his/her character. Puzzles should be used if you think it would be just too easy to roll a skill for it and figure out a troubling mind boggler without much effort. He/she/they might be able to sit down and try to figure it out as you play with someone else in another place. Or you could end a game play with a puzzle of some sort that they'd have to figure out by the next time you play.

The one thing you should be very cautious about is that it works. The solution to this puzzle must work for your story to be valid. If there's a hole in your puzzle and they pounce on it right away, all you can do is say, "Oh, yeah. Uh. Good point. Well then. Uh..." and you're screwed.