Maybe say you want to keep your work relations strictly professional

Thank you for the invitation, I don’t participate in religions and prefer a more spiritual approach, have you ever taken a bite out of a still beating heart? I’ll clean out my desk.

A well timed fart is effective.

My standard work response is "I'm not religious". If pressed I say something like "I'm not religious, although I have my values and beliefs. But one of my rules is to never discuss politics or religion at work.". I feel that, in Texas, being to vocal about athiesm at work could damage my career. And I have a family and can't afford to be out of work.

My former employer, shortly after I started work there (at a PR company), wrote a press release for a special speaker, at a small, local Bible church for the venue. She nonchalantly invited me to go, as it was open to the public and there was no admission fee, and I didn't know the speaker but figured I'd go and see what the fuss was all about. After all, this was a special presentation and it was bound to be a unique experience. So I attended and — surprise! — it was nothing more than a regular church service. It was a fire-and-brimstone sermon, with all the trimmings (including yelling at some kid who wasn't taking it seriously enough). And it turned out this old guy wasn't some special speaker, but a regular minister — intimately knowledgeable of this church congregation, because he immediately recognized that I wasn't a member of the church as I left the building at the end of the service. (Yes, I stayed the entire service to be polite, though in retrospect I should have left as soon as I realized it was a church service.) I wasn't angry, exactly, but I was annoyed at the conversion attempt my employer made. It was deceitful and underhanded and I felt rather disrespected. I spoke with my boss about religion occasionally over the years after that, and my irreligious position was well known (as it had been from the start), but she knew better than to invite me again. I think it was quite obvious in my body language that I was displeased with her manipulative attempt at recruitment.

In a similar situation, I let them know that my spiritual life is private & I do not discuss sex, religion, or politics in the workplace. I thanked them for understanding & wished them a good day.

Since I live in a right to work state, I made a point to document everything via email to my work account with a cc going to my personal account so if I had to deal with HR, I had date & time stamps.

I got a promotion to a different area but kept my documentarion, just in case.

I'm a stateworker and my boss knows to observe the wall of separation. It's a non-issue. If he ever did, I would remind him of that requirement. If I worked in the private sector, I would respectfully decline the invitation.

I've always said, "I'm an atheist, but thanks anyway for the invitation."

I'd politely refuse.

I would just say Thanks for the invitation, but I do not go to church.

I will simply say, boss need to start being professional or I will tell on him/her to his/her boss.

What do I do before or after I get fired? ?

Give him a copy of the rigveda.

I just attempt to politely excuse myself from the conversation as a evil and go back to doing my job

I really don't have a good response to this since it has never come up. But to be honest, I would try to let them know that I'm not a believer. easier said than done i would guess.

Never been an issue because I work weekends, but I'd just tell him no.

I hope you won’t have a nasty situation, but you might. Best luck!

Tell them to fck off with a smile

Give him a copy of Why I Am Not A Christian

I've always lead with "I'm not religious and I'm interested in talking about it." My co-workers usually take the hint.

He's the owner of the company. Very nice and we have in common that he plays drums in the church band and I 'used to be' a church organist. (I had the skills and it was a job (and a running profession in my not-too-religious family)) . He wasn't pushy and I let him do all the talking while I nodded politely. Since it's a part time contract position for me I don't feel too much pressure (thankfully), but I was curious how others would handle this type of situation.

Christians are taught to spread the word and convert us heathens and sometimes they really take their job seriously.

The practise is called force recruitment and is illegal under the employment standards of most Canadian provinces, it is consided to be workplace harassment.
Too bad you live in a backwards nation, all you can do is tell him that you consider your beliefs a personal matter that has no place being discussed at work and hope for the best.

Be honest with that person. They can't fire you for what you for what you believe in. If do it in a peaceful manner.