In real life?
I generally set aside our differences to focus on whatever brings us together - work, volunteering, etc. - so I generally don't engage with their religious beliefs at all.
If the other person makes it known that they're very religious, this will generally create a mental distance between us. I'll still try to be pleasant, but I won't try to make them my friend.
If they go a step further and express religious beliefs that I consider immoral - opposing same-sex marriage or abortion, for instance, or racism - I'll generally just avoid them.
And if someone in a social setting is using their religion as a crutch, I'm not going to try to kick that crutch out from under them. For instance, if a widow I know socially keeps going on about how she's sure her late husband is in Heaven and she'll see him again someday, I'm not going to try to correct her by telling her that Heaven is made up and her husband is gone for good.
Now... I do think Heaven is made up and her husband is gone, but it would be pretty tactless to bring it up uninvited in an everyday conversation.
Basically, in real life, I will generally think that religious people are wrong, but I don't make it my mission to correct all the wrong people I meet.