"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 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.

I never tell them

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 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.

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’m from the Philippines and majority of the population here is religious... i just simply say “I’m an atheist”

I just tell people that I am an atheist and of course they try to convert me every time I tried to be as polite as possible and tell them that I have no interest in their imaginary Sky Daddy

I usually just tell them if it comes up in conversation. I do enjoy some of the looks and comments I get.

I CANT and it is smart of me to not to

I just tell them that I have never seen any proof that God exists. But they can believe in what ever they want too!

I've managed to say that openly only in America, I had to pretend I was christian in Greece so i wouldn't get deported. I live in N.Y. now so it's not that big a deal but even when I lived inn Oklahoma I still said I was an atheist to my x boyfriends family that his dad was a Baptist pastor. His father said nothing but his mother tried to justify my xs' behavior by bringing me some books about why we love men that hurt us and it was basically justified by the bible or some other crap like that, I didn't bother reading it. But here in theUSA I've had an easier time just saying hey I'm an atheist I respect your right to believe just don't shove it down my throat thank you

I tell them out-right that I am an Atheist, I make NO bones about it all, BUT they do get quite a Surprise when I also tell them and SHOW them that I have a Doctorate in Theology and Comparative Modern Religions AND still remain an Atheist.

sometimes there are friends who'd invite you to some religious meeting or such and I am like "that's good bro I guess but, I don't believe in such"

i give them time to talk i just beleive what i think is true in my mind

I tell them that I am not a believer and that I have my own faith (in the secular meaning of this word)

i think my feelings r private to me how i feel should show by how i live

I tell them I’m an atheist. If they cannot accept that simple statement, well, then the conversation comes to a quick end. I don’t fault them for their beliefs, as long as they accept that having differing opinions does not make someone a “bad” person. Just, please don’t tell me that “some day you’ll see the light.” I do not express condescending attitudes towards theists, and I require the same consideration from them.

If the subject of religious beliefs comes up, I'll usually just say that I'm an agnostic and don't subscribe to any particular religious dogma. I'm spiritual in that I have an awe of Nature and a wonder about our Universe and the other "Big Questions," but unless somebody seems to want to discuss that topic further, I don't push it.

If they are not completely mindless and if that is where the conversation is headed I will tell them. If I think they'll listen I will further explain myself. This is kind of like coming out of the 'Atheist Closet'. Not as threatening as coming out in the traditional sense though.

First, you get a bunch of balloons and confetti, bust through the door and go, "surprise! I'm an Atheist! Wooot!"

I'm being silly, but if that is your style, go for it! Lol! Here is my thing, I don't tell them unless they ask me. If someone was Christian and you're having a casual conversation or first meeting, did you say "Oh, I'm a Christian by the way...could you pass me the ketchup, please?" That would be quite odd. I find that when you just tell them up front, it makes it seem like you're one of those crusaders carrying a banner and charging in on them about to challenge their beliefs.

What I've done is if the topic ever comes up and they inquire, because it eventually comes up, I wait for the opportunity to arise and then tell them I'm an agnostic...or in this case, you'd say you're an atheist. Then the look after you tell them, rather than their words, will tell you how they'll treat you fro then on. I live in the South in the US and I tell ya, they assume that everyone is Christian or religious. Then, when you tell them something like, "I'm agnostic" they automatically think it is the same as an atheist. Only if they're open to allowing me to explain things to them, will I tell them the difference.

I just tell them I'm not religious

I still avoid it, don't want to start fights.

If I'm at school they can usually tell from the FFRF and SSA stuff I have on my backpack and laptop. If we are talking about religion/politics I don't shy away from saying "Yeah no, I'm an Atheist so using the bible to justify X doesn't work for me".

It depends on who they are to me and what the situation is but I generally don't bring religion up. But if I'm asked, I'm honest and share my beliefs. I might also ask them what they believe about God. I've never gotten the same answer.