I agree with Dread_Zeppelin in the sense that it's counterproductive to try and open a dialogue with an atheist when it is clear they are not receptive to hearing from you on the topic.
I have seen situations on this website and in daily life when people have done it anyway and when they've made the person angry they've then responded with what seems to be a standard reply 'I tell you the truth and that is how I help you', and that logic seems to shield them from seeing they have just pushed someone further away from the faith, there are times when speaking can do more damage, regardless of what you are saying.
In many cases atheists are arrogant in their belief because allowing themselves to consider the possibility means opening up to so many things that were never an issue, anyone formerly of that view can understand that massive change follows and many atheists disbelieve simply out of fear of facing up to who have they been.
As many people know fear can cause harsh reaction because it is a defense mechanism, so we need to realize that coming at atheists in such a direct manner will only make them push back and it can provide affirmation for them.
It is tempting to take the direct root and act now so not to waste time but so many people who have gone from atheism to a strong faith look back on their lives and see how separate events contributed to them turning to faith and away from their former, often destructive life, and so without those events they may not have found their way, it is sometimes best to allow people to continue making mistakes and just be there for them as we all need to experience these things for ourselves to truly understand.
Some people will hear the word of God and have a moment of revelation, others come to faith over time after learning, as a Christian one of the great challenges is to find the right approach for the right person so I would say there is no one way to approach or deal with atheists, just get to know them and you will get to know what kind of help it is they need.....see them as a person...not a project.
Great Post!