1. Open the door.
2. Discover that the door knockers are, indeed, religious nutballs.
3. Close the door.

That's about it.

(BTW, Step 1 is optional.)

We had an old man called Jim who used to come to our house probably twice a month, my Dad invited him in and he'd have a cup of tea and tell a couple of jokes and chat about some general topical theme, then he would find a passage in his bible and try to apply it and we'd maybe disagree or maybe politely listen, but we understood that he felt it was his purpose to teach us but otherwise he was just a nice old chap who came for a chat and a cuppa. He knew we didn't believe and didn't push it, and we knew what he believed was bollocks but we didn't push that either.
I think the best thing to do is realise most people are just trying to do good in their own way and be respectful, if they're a dick then you don't have to talk to them again do you?

We have been blacklisted by both and 7th Day Adventists.

Super soaker?

I would say, you knocked on the wrong door. Then just said, have a nice day and shut the door.

One time I had some religious nuts show up on my property. I said to them, "If you don't leave, I will call the cops on you." I never seen them sense.

Ha, an old girlfriend of mine answered the door naked and invited them in.

My most successful strategy involved answering the door shirtless brushing my teeth. There was about six inches of snow on the ground and I just stood there blocking the door brushing my teeth until the guy just left after a minute or two. He never came back.

I reverse the the position, I take out my bible that has has tabs to the scripture I want to discuss with them. Such as how rape is considered a crime against the father instead of the victim. The I try to go to the actual human sacrifice that is in the OT.

Some of the young mormons have tried pascal's wager, but you can see their the smiles leave and you show them its really not a binary wager.

Right now, I think I have been black listed from every religion in the area.

My mother is a JW and they have a 'No Call List' just ask them politely but firmly to be put on that list and they will no longer call on you. If they do then just mention to them that you have already politely asked them not to call on you and that you would appreciate if they would respect your wishes. Sometimes they check just to be sure that you really, really, really don't want them trying to save you before Christ and his Angels come back and slaughter all the non-JW's until the world runs ankle deep in the blood and guts of the 'worldly' people who did not heed their call. I know, it's seriously fucked up but what do you expect when dealing with religious crazies?

Tell them you are an Atheist. It has yet to fail me.

I’m a confirmed INFJ/ introvert. I don’t answer my door, unless it’s family; they text first. I don’t answer my phone, either, lol. Same criteria.

I would always prove I know more about their religion than they do. Then convert them away from their fantasies, into reality. They don't come to my door anymore.

I just say I'm not interested, and close the door in their faces.

Keep your front door locked. If you do not know who it is, do not open the door. If it's my mother, do not open the door. I keep a baseball bat right where the hinges are.

Once I yelled over my shoulder "is the chicken sacrifice ready yet?" They left right away.

Don't answer. If I'm not expecting someone I likely won't answer the door.

My front door isn't obvious so I don't get door knockers, I barely get any post!!!!!!!

That is exactly the way I deal with them. If I have friends over, I invite them to join me. I have not seen the same ones twice. In fact, I haven't seen any in several years.

I have a sign on my door that's a picture of emptily smiling people, one holding up a bible, in a circle with a line through it. Haven't heard from them since I put it up about a year ago.

That wouldn't put them of.A swift kick in the genital region works a treat.

This remembers me of a time in my younger days. JW would come knocking on the door every saturday morning. If you have ever gone clubbing the night before early morning visitors are not on your top ten to do on a saturday.
One saturday i was so pissed off i look them straight in the eye and told them i worshiped the devil.
They never returned..

I wish I had this problem. The only proselytizers I've ever had to deal with ambushed me after a fishing trip, walking back to my car. We got to talking about the old testament. That worked for me; they really knew nothing about it, only carried the new. They couldn't address any of my questions, so eventually had to move on.

They stopped coming around my way after stopping by and being invited in to blaring black metal, not satanic (too gimmicky), but nature oriented lyrics. I was told that I was a heathen and I was going to hell.

Meh.

depends a bit on your objective. do you want them to stay away, do you want to make unbelievers of them, do you want to waste their time so they aren't pestering someone else?