Here are some brief arguments some people made about this topic:
Think of an old building, how did it get there? Someone built it, even a child knows that. But how can we be sure, we never saw the building being built, but we still know there was a builder. A painting, how did it get there, a painter painted it. What more proof of a painter would you want than a painting?
Then he made some stupid arguments about bananas and stuff.
The other guy (Athiest) was saying:
Everything needs an enviormonet to live in, God doesn't have one.
Other stuff about praying, people doing good/bad acts in the name of god.
Can God create a rock that is so heavy he can not lift it etc.