So far, I've written about how to discuss Islam with Muslims, and Christianity with Christians. So how should you proceed if you're a theist and you want to discuss your religion with an atheist.
I have a few tips for you.
First, a definition. Atheists don't all believe that there is no god. here's what atheism is. You say there is a god, I say "I don't believe you". Notice, "I don't believe there's a god" is not the same as "I believe there is no god". I suggest you meditate on that until you've grasped it, because it could become crucial. See, if someone "doesn't believe" then no faith is needed. And, by the way, atheism isn't a religion, it's a lack of religion. If atheism is a religion, then not-playing-golf is a sport.
1. Don't threaten him with hell. That's like threatening an adult that the Tooth Fairy won't leave him sixpence. Also, Pascal's wager won't work (see part 2 of this series).
2. Don't use any personal revelations you've had. You might find them totally convincing, but they were revelations to you; the atheist didn't get that revelation. If you nearly died and saw Jesus, I can't tell you what yuo saw. But it was your vision, not mine.
3, Don't cite the power of prayer. The atheist will explain that praying to your god is as effective as praying to a china teapot. The answer will be "Yes", or "No", or "Wait". And because we're talking about real-world effects, it's possible to measure them, and that's been tried, and the result is "Prayer does nothing"
Worse than that; every time there's a flood, or a hurricane, or a mass shooting, politicians send "thoughts and prayers", and atheists see that as a way of doing nothing whatsoever while appearing to be doing something.
4. You can try "Someone must have created the creation". But the atheist will first object to your use of the word "Someone" and then the word "created" and then "creation", because you're assuming what you're trying to prove. You'll get more respect if you ask"What is the origin of the universe", but don't be surprised if you get the answer "I don't know. So what?" however, some atheists will have five possible answers, and say "I don't know which of these five is true, but your god-did-it is a sixth"
5. Ditto evolution. If you want to rubbish evolution, then the first thing you have to do is learn what it is. If you learned about evolution from your church or mosque, then it's almost certain that what you were taught was a completely ridiculous scheme that *no-one* believes. There's plenty of internet resources where you can learn what the theory really is, and then you'll be able to argue against it without looking a complete fool. Oh, and if you say "If humans come from monkeys, why are there still monkeys" don't be surprised when everyone laughs at you. Find out why that isn't a sensible question.
6. Where to your morals come from. That's a good question, and worth debating, but many atheists will throw slavery into your face. The Biblical morals allow slavery, and that's a definite no-no today. So how did you determine that slavery is evil? Not from the bible. So you have to use something in your head to decide which parts of the bible are moral and which are not - so what is the bible actually doing here?
7. The fine tuning argument. That's a good one, and many atheists won't know how to counter it. Unless they've read my blog and see the two ways that you can counter the fine tuning argument.
8. How did life originate? This one will stump pretty much every atheist; he'll have to say "I don't know". But if you say "God did it" then you have the problem of explaining how God originated. This one is, however, quite a good point to debate. The technical term for this is "Abiogenesis" and it's worth googling before you start, so you know what the atheist might try.
9. Don't lose your temper and start swearing at him or insulting him. For example "Atheists are sad, lonely, angry etc etc " When a Christian does that to me, I tell him "You're a Christian, aren't you. I can tell." Which isn't really an insult, if you think about it. Or maybe it is, your call.
10. Argument from complexity. For example, the human eye. How could something so complex have evolved (don't say happened by chance, because you did mug up on evolution like I said in point 5, didn't you?"). What you're looking for is something that is irreducibly complex. Which couldn't work if it's only partially there, the full thing has to be there. Half an eye doesn't work. BUT. Here's a tip - the eye isn't going to give you irreducible complexity. You'll need to find something else.
So, good luck. There's lots of atheists around, and many of them will be willing to discuss atheism with you.