Long term advice when debating theists.

[Polaris]

Don't expect theists to fit a stereotype you have encountered. As a theist myself, I have only ever met one person who told me the Earth was 6,000 years old and wouldn't have known anything about Creationism had it not been for atheists beating straw men.

Think of the theist as just like you with a different viewpoint. You both like hot dogs, but you may like catsup and they like mustard.

[Brian37]

Don't expect theists to fit a stereotype you have encountered. As a theist myself, I have only ever met one person who told me the Earth was 6,000 years old and wouldn't have known anything about Creationism had it not been for atheists beating straw men.

Think of the theist as just like you with a different viewpoint. You both like hot dogs, but you may like catsup and they like mustard.

Who is saying theists believe the same thing? No one here is doing that. Actually it is precisely the fact that even within the same religions no one can agree on the "interpretations" of the same books, would or should indicate that those books contain no insight to the nature of reality or our species behaviors. The only thing those books reflect are the beliefs and social norms of the people who lived in the time they were written.

There still are people who believe the sun revolves around the earth. There are still people who deny evolution. If you are going to argue sample rate then don't ignore it yourself. I have been at this 14 years and there are stupid people in religion that dwell on fairy tales and superstition and literally believe the fantastic claims in the bible. The two most important stories, the birth and death of the Jesus character alone are negated by modern biological science. It takes TWO sets of DNA to make a baby, and humans do not survive death.

[Cephus]

I've always thought the science/origin argument that usually results from the debate is a goofy one to partake in for the Atheist.  Because the atheist flat out doesn't know what happened, and the idea of something creating the universe just isn't absurd enough.  Similarly the idea that there is some order and purpose to the universe is also not that absurd.  
The harebrain schemes attached to said creator, however, with all the heaven/hell stuff just doesn't make any sense.  It doesn't make sense in so many ways, that it's really indefensible.  I suggest skipping the "How'd we all get here then!?!?!?! " And "Intelligent Design needs an Intelligent Designer!!!" because both of those are really irrelevant to religion, which is about what God wants us to do, not how the universe got here.

The thing is, the atheist doesn't know and neither does the theist.  Just because someone is uncomfortable not knowing something isn't license to just make something up out of whole cloth, which is exactly what all religions do.  Pointing this failure out doesn't change anything though as all religions go from A to a ridiculous, irrational leap to B, made entirely without any objective evidence and a lot of emotional demands that it has to be true because it makes them feel good.

Most theists are just idiots.

[Minimalist]

Don't underestimate a theist based off stereotypical notions you have...

Correct.  Underestimate them because they are adults who think they have an invisible friend.