I don't go out of my way to speak to athiests but when they do ask me a question about the existence of God I think John said it well...
"It's pretty easy. Where did all the stuff come from? Either Someone very smart and powerful made the stuff, or the stuff made itself. How can stuff make itself? If you believe it did, then prove it, show me."
In so many words, that's what I will talk to them about because in no way are they looking spiritually with spiritual eyes. I just approach it from the type and shadow physical side.
I basically tell them a story and place them in it...... "If you were an astronaut and you flew to Pluto, and after you landed, you jump out of the shuttle and on the ground is a swingset (a kids play toy, or whatever). The first thing you would logically think is.... 'Someone has been here before me and made this and sat this swingset here on Pluto'.
It's the same with any object you see or hear or feel or smell or taste. It has an origin. An originator. Stuff doesn't make itself. There is some grand intelligent being that started all this. It takes power and intelligence to create anything.
That's how I start out. You can't explain to them the circle theory, the circle theory doesn't explain anything.... that such and such created such and such and so on and so forth, rubbish. THERE IS AN ORIGIN. There HAS to be an originator for ANYTHING at all to exist. Logically, there has to be a Beginning.
I remember, I spoke with an athiest one time and he said... "Okay, I get that, but why would an originator create all this death and pain and suffering? Why burn everyone in fire forever for not believing Him and then call Himself love?
THAT, I think is the real issue athiests have with religion. Most religions teach that if you don't follow their ways you get punished forever or destroyed. Then of course you give them the gospel of the kingdom... the old man and new man. knowing good AND evil, you can't have one without the other etc... If they logic this out, and of course God's spirit is working in them, they will begin to understand.
In the past athiests use to argue and argue with me and I use to give them the same christian orthodox answers, "Well, they will burn in Hell forever, etc..." No wonder they would argue with me. My explaining to them that God is love but will burn most people DID NOT make sense to them. I was just parroting what I had been told believing it to be right. Thank you LORD you pulled me out of that.
To me, an Athiest is a person who believes there is no God. Logically, it's not possible to consider yourself an athiest. If they base all they know on "sound logical princibles" then they would have to call themselves a Agnostic. Which means, they don't know whether or not there is a God, there may or may not be one. You would have to know all the knowledge in the universe to logically call yourself an athiest.