决定谁先召唤血腥玛丽。 轮到你的时候，走进浴室，关掉电灯。 看着镜子，口中重复三遍“血腥玛丽”。 如果血腥玛丽没有出现，就原地转3个圈。 吹灭蜡烛，离开浴室。

I'm interested in that, but I only have a few mins. Can you give me at most the first 500 characters of a detailed explanation in English about that?
If no one volunteers, play a quick game to decide who it will be. Flip a coin or play rock, paper, scissors. Whoever loses goes into the bathroom first. Close the door behind you so it’s completely dark. Make sure no one followed you in. You have to be alone when you call Bloody Mary.  Place a candle on the sink in front of the mirror and light it. Don't have a bathroom you can play in? Try summoning Bloody Mary in another dark room with a mirror. Keep your eyes open when you’re saying it. Make