I recently ran across this article on WikiHow. The entire thing is fairly funny, but my favorite part is the very first step.
Are you prepared? Most Atheists are highly intelligent. Probably better educated than you are and have spent a lot of time thinking about reasons TO believe. You have to give the a real reason - not just an emotional one! You need to read and think a lot too. Don't be surprised if they manage to persuade you to give up your beliefs.
Not only is that a very telling word of caution, it is absolutely true! As a Christian teen, there was always a bit of hesitation in the back of my head, as though I were subconsciously aware that something did not add up. My church and parents, to their credit, did encourage thought and, to some extent, doubt. They said that if something is true, then it will stand up to scrutiny. They were right.
I never took the time or trouble to actually unpack my beliefs, so my fear of losing faith really was subconscious. But now, I can safely say that I am very sure of what I believe - with regard to religion and god, at least. There is not a chance that any Christian - no matter how nicely they ask, no matter how aptly they can quote Proverbs, no matter how many pancake breakfasts they take me to - can make me change my mind.
This is not because my mind is closed, but because I know what they are going to say. As you have seen, I am obsessed with atheism and read all kinds of articles and books on the subject. I don't read many books on religion, because they tend to jump straight into the Bible, which I don't take seriously and the whole thing gives me a headache. I do read articles, however, and nothing I have read has brought me any closer to accepting the lord jesus as my personal savior. I am, for the first time in my life, on completely solid ground.
As I said, I am not close-minded. I say that you cannot convince or convert me because I know what you are going to say and all of the arguments are false. That does not mean that I am unable to be convinced, however. What I require is true evidence. Something new, something that cannot be explained otherwise. If God is real, that shouldn't be too difficult to find. I mean, what kind of loving god makes himself so difficult to see? And if he were so intent on making his glory known, why would he create a world that looks as though he wasn't there at all?
Find this evidence for god, then come and show me. That is how you convert an atheist.