As long as there has been belief, there has been unbelief. As long as there has been theism, there has been atheism. But no one is born an atheist. It's a choice a person makes to follow a certain belief system, and so requires a certain amount of faith, just like being a Christian does.
That means Christians don't need to be intimidated by atheists. In fact, we only have to look at how Jesus interacted with Pontius Pilate to see how we are to approach them. When Jesus was unjustly arrested and dragged before Pilate in John 18, He faced a man who seemingly held all the cards. But this moment was part of His plan; He had predicted it all along (see Mark 10:32-34; John 12:32-33). Despite being bound and beaten, He was in total control of the situation.
Jesus wasn't intimidated by this unbelieving cynic, because He saw God's supreme plan unfolding. We can be confident in the same thing when we recognize three things: our inadequacy, God's sovereignty, and their necessity—that is, the fact that atheists need Jesus as much as anyone else. We can proceed in any encounter we have with an atheist knowing that God has prepared that encounter.
Atheists don't have the plague; many of them just have questions. When Pilate assessed Jesus' threat level by asking if He was the King of the Jews, Jesus responded in an equally reasonable way, attempting to determine why Pilate was asking (see vv. 33-38). If we do the same, we may be able to determine if an atheist holds their position based on critical thinking or if they're just jumping on the bandwagon of moral convenience. You can find that out by asking and fielding questions.
And when it comes to responding to an atheist's arguments, don't worry about giving flawless answers. Even if you don't articulate the perfect response, you might be planting a seed. Your job is to obey God's calling to share the truth as best you can and then let Him take care of the outcome in a person's heart.
Remember, you're not God's guard dog. You don't need to berate anyone with whom you disagree, even though you should be prepared to address common questions an atheist may pose. Instead, be respectful, keeping in mind that it's ultimately the Holy Spirit who will convict a person's heart and win them to Christ. Better to lose an argument with grace and keep the door open to future conversations than win the debate but lose the soul.
So be ready to explain why you believe what you believe. Let the Bible guide your talking points. You're not deciding what truth is (as many unbelievers try to do themselves); you're just representing what God has said and done. If you're secure in what you believe to be true, not only are you less likely to stumble in a hard conversation, but you're also more likely to maintain a respectful and kind attitude.
Jesus, despite Pilate's skeptical attitude, stuck to the truth of who He was and what He came to do, and He did it all without losing His cool. As you reach out to an atheist in your life, you might get rejected, or you just might be surprised by what God has in store.