A smack in the mouth is normally effective but may cause offence

Just tell them you’re happy praising Satan ???

My neighbor tried that about a month ago in my house. I was not in the least polite with my response.

Be very quiet and when they ask you why you are quiet just say I enjoy watching people making fools of themselves. I am an introvert an this works well when I am asked why so quiet.

Would depend on the context. If it is some random stranger who feels like proselytizing, it depends on my mood if I try to run their brain in a circle by questioning their beliefs or just tell them they are barking up the wrong tree. If it is a casual relationship I tell them I am an atheist. Then the ball is in their court - if they want to have a civil discussion about that, I will - but if they become uncivil or push their preaching harder they've forfeited their right to be spoken to politely. If it is a close relationship... well, they know better. Either they are worried for my immortal soul, or they are looking to ruffle my feathers. Again my response depends on the situation.

You might say: Would you please stop preaching to me.

I find the phrase, "Blow it out your ass" very useful.

literally ask them to stop.

Can you trump on demand? Followed by "That's what I think of that bollocks".

I don't tell you what to believe, so you don't get to tell me....simple as that

Theres no polite way to tell someone to fuck off.
I'll stress it needn't be said with exasperation or anger.
A smile, laugh ... "Oh fuck off with that shit".
Added adamance as required.

Depends on their style. Calm and gentle - I engage in debate. Loud and pushy - I talk about how I love masturbating. And that seems to hold them for about half an hour.

There probably isn't a polite way. I usually just excuse myself and say that I do not discuss religion.

Fuck Off,I Hinted!

I try not to engage by deflecting to a different topic.