The three main strategies that prominent atheists use to de-convert believers.

1. Ridiculing beliefs.
People like Richard Dawkins, Sam Harris, and the late Christopher Hitchens prefer to use unapologetic ridicule. They mock flaws in the theology, morality, history, and confidence of believers.
Pros: This approach is the most controversial and therefore puts atheists directly in the public eye. They end up on news programs for interviews and fill auditoriums for debates. The approach also works well with actual de-conversions. I should know because this very approach is what contributed the most to my atheism. As a confident believer, I felt compelled to prove just how wrong they are. They must be wrong because their accusations are so ridiculous! It caused me to research my position and when I fell short time and time again, I realized I was tricked! I see what you did there...
Cons: This approach certainly doesn't help the image of atheists in the public eye. The people that aren't won over with this approach will often double-down on their religion. When they see a battle line drawn and a vocal opposition, they run back to their team cheer louder than before. Also, the people without a team may come to negative conclusions about the moral fiber of atheists so willing to piss people off.
Recommended reading: The God Delusion and God is Not Great.


2. Educating with science.
People like Lawrence Krauss, Bill Nye, and the late Carl Sagan prefer to educate people. They see the problems that religion and superstition cause for mankind, and they believe the problem will solve itself with scientific literacy.
Pros: Ultimately, as people come to understand the grander alternative, their old myths seem petty and uninspiring. This is the least offensive method because they usually aren't directly telling believers they are wrong, just slipping in an alternative. At some point down the road the believer will compare Genesis with cosmology. They will contrast creationism with abiogenesis and evolution. They will juxtapose a world made for them with a vast universe in which they are a speck of a speck. There is a beauty and poetry with this approach. The other two approaches may leave a certain type of believer feeling fearful, alone, and without purpose. Science fills the holes left by religion, so it's a less intimidating transition. Ex-believers feel more inspired, more joyful, and yet more humble than they did with their old myths.
Cons: This isn't a quick process, and there's no guarantee that they'll actually confront their cognitive dissonance. There are plenty of authors out there seeking to harmonize science with religion. Believers may get stuck in this thinking because they aren't pushed or challenged further. Another problem with this approach is people often replace their established religion with a pseudoscience or spirituality. (Especially if the believer doesn't develop a skeptical mindset)
Recommended reading: The Demon Haunted World and A Universe From Nothing.


3. Undermining "faith."
People like Peter Boghossian, Michael Shermer, and Matt Dillahunty attack how and why believers know what they know. They reveal to believers that their faith isn't a virtue, but rather a way they pretend to have knowledge they actually don't.
Pros: People are shown that hope and faith are not synonyms. Faith is a knowledge claim for topics where evidence is absent. There is less preaching and more inquiring. How do you know Jesus is real? and How do you know the Bible is more reliable than the Koran? and How much time did you spend ruling out Buddhism? They nudge people toward the cognitive dissonance they didn't know they had. Believers confront their own beliefs. They begin to examine why they believe in cultural, evolutionary, and psychological contexts. They examine the relationship between evidence and knowledge.
Cons: This approach is offensive to people who fundamentally disagree with the premise. Some people love their faith. They depend on it to get them through the day. Faith feels like a safety net. Whether the believer has fallen on hard times or has a depressing fear of death, they would rather preserve that safety net - even if it means maintaining ignorance. Attempting to take that away can be taken as a personal insult.
Recommended reading: A Manual for Creating Atheists and The Believing Brain.


All three strategies have a place in public discussion. Where one approach fails, exposure to another may succeed.