The best mystery I have read was “The Speckled Band” I find that the author did an excellent job at making the reader wonder and actually look deeper into the story instead of other mystery books who give bigger chunks of clues that make it more obvious.
A starter for one of my mysteries might be something towards the lines of: One dark and gloomy night, I was walking through the ally way and I heard a weary scream. I scarcely looked around my surroundings and began to wonder. Where had it come from? What had happened? Could I myself be in danger?