How do you know you are a Christian?

I remember when I was much younger in church, sometimes they would ask if you are a Christian raise your hands up. Almost everybody hands in the room would go up without hesitation. I always wondered then, how they knew they were Christians? Recently, I was discussing with someone regarding the subject matter of how do you know you are a Christian and I decided to share it with you all. If you are a Christian, how do you know you are?. Share with me.