My experience has been varied. Having a solid grasp of the most common attacks on the faith and how to respond with a solid apologetic is useful. But for me the primary usefulness of that preparation is that it helps me keep from becoming defensive. If you have nothing to hide from and nothing to prove to yourself it really lets you focus more on the person you're talking to, the situation you're in and what God might want of you in that situation. I really can't think of anytime when what was needed was a defensive, dismissive, angry, condescending, or judgmental response...but all of those are common to our nature. If you don't want those to be you, then know your stuff and respond with gentleness and humility. God doesn't need defending. It's our own egos that need that. We're not ambassadors because we deserve some sort of ambassadorial respect. We are ambassadors precisely because we are just as undeserving as the people we reach out to.
Some questioners may sincerely want to know how you deal with Dawkinsian angry skepticism or just the problem of pain. Having a ready response a la 1 Peter 3:15 can lead to a really great enlightening and encouraging conversation.
Some merely want to be argumentative or competitive. In some situations jousting here and develop camaraderie when it's done with respect and good humor, other times you just have to know when you're "being trolled."
But the majority I have talked to have a really heavy emotional component to their atheist identity. They earnestly do not want the Christian God to be. It may be deep guilt, perceiving the distance between what their life is (or the life they desire is) and the life they ought to live. It may be deep anger over hypocrisy or having been personally injured or manipulated by people in the church. It may be deep fear of admitting the possibility that people they knew and loved deeply could be in hell. It may be fear of facing the possibility that they have taught a lie to others and done their best to push them away from the truth (no pastor who has had a change to his theology later in his work is a stranger to that terrible feeling). These sort of deep wounds fester and grow adding new perceived hurts, injustices, or guilts until the mind is willing to do anything protect itself from that reality. These folks tend to get heated pretty fast and arguments are too risky since it's too easy to just pile on more hurt. People break things, broken people need help from the One who is more than just a person.
Productive conversation in those cases is usually achieved by surrounding the situation in respect and appreciation for the other person. Take them out to lunch. Take a little time to enjoy their company. Then when God is ready to start dealing with some of those wounds you're in a position to talk with some latitude for mistakes since "love covers a multitude of sins."
Once finally talking, usually some for of the apologetic from morality is what sticks. It's the most personal, and once heard it has to be weighed not just by logic or emotion but by the conscience which is the realm of the Spirit that can actually deal all of those hurts.