It usually starts with a laugh, or a side-eye that lets them know I'm skeptical about what they're telling me. Then I just say it, "I don't believe in that stuff."

I tell them directly that I have never accepted Jesus as my savior; nor do I subscribe to any other religious teachings. I mention that scientific method suits me; and therefore anything less is merely supposition or opinion.

I sport many ill religious tees. As religious wing-nuts have begun an assault on our secular commons and me a studied theologian of hermeneutics, I enjoy Socratic dialogue. The look on their faces when they see reason coming into the picture, as I quote the Bible and say, 'I hate what you have done to my Jesus.'
As an atheist this blows their mind. I tell them I'm here to rescue the Jesus I admire from the eternal Pharisees/religion & Gov.

I never tell them

I don't know that this is hugely helpful but I think it comes down to what your comfortable with, if you know the people you want to say it to then you're best placed to judge how they would take hearing it and whether or not you need to wrap up the statement in anything else to soften it.

"Oh, I don't believe in your god, but thanks"
I don't believe in anybody's god, but it's nice to add that extra little tweak to make them think, even fleetingly, about the idea that other people believe in different gods.

I live in the bible belt, and for the longest time have hidden my atheism, when people start talking about Jesus.
I still keep my mouth shut, unless directly asked. "You believe in Jesus, right?" "--No. I'm an atheist."
I don't get asked much, so I don't have to out myself much. Most Christians assume that everyone agrees with them, and most of the time they don't expect, or want confrontation any more than I do.

Inspired them through the ideas put forward in the discussions

I don't really have a problem telling them , sometimes it can lead on to some very interesting conversations.

I slam their religion without mercy and give examples of why their respective religion is crap.

I always tell so they know not to bother me with religious doctrine. If they don't want you around anymore they are not worth your time. Telling you are not a believer can actually get a lot off pressure off you. You don't have to feel uncomfortable anymore when certain topics come up. You can give your opinion freely.

Definitely, tell them. Spread it as far and wide as you can. Who knows? Maybe they will come out as an atheist as well.

I think it's irrelevant. If they don't ask, I don't tell.

Did tell my sisterthat, if I'm going to christian hell, i'll have plenty of Christian company. That usually ends her judgement.

Don't. Not worth the drama. My motto, live and let live.

I'm blunt and tell them right away. I don't BS about it. My whole work and family know. Respect the believer, NOT the belief. I learned that.

You don’t really need to tell them . I’ve worked very diligently at being able to talk to people without that being a issue. I’ve learned to focus more on them when discussions of that nature come up. When proclaim this, or that all we do is help promote division , this makes it difficult to communicate. I put humanist in my profile because something had to be there .

The subject rarely comes up, but I generally just tell them flat out. Which inevitable leads to, "I'll pray for you." I always reply, "I'll write a letter to Santa for you." They tend to shut up.

Generally I find people tend to keep their religious orientation to themselves. Therefore I'll only reveal my atheism on a case by case , need to know basis.Sometimes I feel comfortable to reveal my beliefs and other times it feels more appropriate to keep them to myself.

Australia, where I live, is supposed to be a christian country too, and like the U.S. different states are more so than others. I am up front with people about the fact that I am an atheist, and if they want to know then I tell them why.
I tell them I have studied theology at university level, as a committed christian, and came away realising that it is based on MYTH at best, and at worst it is simply outright creative fabrication for political gain!!

I usually keep it to myself. Eventually they get the picture and either keep me as a friend- however misguided, or shun me. If they do ask me outright I answer honestly by saying: "I believe in science, reality and having fun!"

Is not a problem to tell them in what you trust ,the complications start when after the question "Why you don't trust in god(the religious one),in jesus etc?"Then you start to explain what you think about their religion and they look to you as an enemy .....Part of the show for me )))

I live in Islamic county and telling religious people my real believe is not a good idea

Why would you even bother? I'm as bothered by that as I am someone telling me that they are a Christian, who cares??!!
What you believe, or disbelieve is about as personal as your sexual preferences. ONLY appropriate in the proper CONTEXT.
That's what's so the matter with us as a species. I'm an atheist...yea me! I'm a Christian...yea me!!
NOBODY CARES......
Remember what your mother told you.... It's impolite to discuss Politics, Sex or Religion

I just walk past them and ignore them, just because I don't believe ion their god, doesn't mean I have to rub it in their faces.