CHRISTIANS ONLY: How do I respond to these comments I receive from atheists?

When I said CHRISTIANS ONLY I meant this!!!! If you are not a christian than DO NOT RESPOND!! Do I have to spell it out for you? Anyways, christians, I am a bit ashamed to say that I have never led a person to Christ. I am being honest and I feel like a failure. I do have faith however and I believe that in time these atheists will realize that I am in fact correct. I have been wanting to be a preacher for quite some time though I do not feel as if I have been at all effective. Do I require more faith or just patience? Sometimes it seems like God is not listening and I know that this is not true for I have read the bible. What do I say and how do I say it? Please help me for I would like to belileve that the lord has a purpose for me.