At Night, go to a dark place outside. It can be a place like a forest or near a shed without lights. Then you whistle the clown whistle.(I will put the vid in the multimedia) If you have done it right you will hear someone whistle back, it can be any tune. Don't whistle too much, cause then you will stop hearing it. Congrats, you have just summoned a killer clown, possibly Pennywise.

When me and my friend did this, it stopped whistling. Soon after we heard a scream and some dogs barking, be careful with this. And we just got a snap from a friend saying there was standing someone near him, not doing anything just staring. So mark my word BE CAREFUL WHEN DOING THIS!!

First book, hope I will succeed with this. Phsyco out!