How do I announce to my family that I don't believe in religion?

I'm eighteen, currently attending college, and in need of answers/advice. My entire family is composed of many religions, but I won't dive too much into irrelevant information of every specific religion. The fact is my family is very religious and denouncing religion—God, Jesus, the Bible, etc.—is just ludicrous to them. I am the first, to my knowledge, to bring such a topic up. I just need some advice to help me summon the courage to explain this to my family. I've have no idea of what their reactions could be since I've never hinted about my beliefs, and this has never happened in the family before. I always "go with the flow" with religion; never believing it, just pleasing my family. Please, help? Any way I can start off the conversation or tips to keep it running smoothly?