A good friend recently mentioned that they were reconsidering their life-long atheism, and asked me what my thoughts were. I'm obvously a non-objective voice on the matter, but I value my friends' happiness more than mere prosletyzation scorekeeping. In that spirit I offer these thoughts on the issue of finding faith, not to try and lure people to Islam but rather to help people who are sincerely ready begin journeying towards God. What path they choose is not my business - it's a supremely personal matter, one that requires a re-examination of all the values and motivations in life. Belief gives a new perspective on every issue, on every topic, on every debate, and anyone undertaking such a journey with sincerity is a courageous person who deserves genuine respect.
Many atheists are perfectly comfortable in their atheism - it sustains them sufficiently. However, someone who is atheist and finds themselves questioning their disbelief has basically run into the limit of what spiritual sustenance atheism can provide. That limit is profoundly a personal one and in my opinion is not reflective of atheism's lack, but rather the questioner's capacity.
But if atheism is insufficient, that does not neccessarily mean that religion is needed! This may seem a surprising position to take for a strong believer as myself, but it is actually consistent with the conviction that religion is unlike atheism in that it is a dynamic journey, not a static one. In that regard, religion is like science - it drives its practitioners forward.
I would advise the atheist to consider agnosticism first, as a means to overcome the limitation of atheism. But then to take the next step, towards actual religion, I would argue that there needs to be a genuine recognition of a void that religion will fill. And the desire to maintain forward motion. The worst thing would be to accept a nominal faith, look up the big answer to the routine Questions (why are we here, etc) and then stop, satisfied. Religion is not atheism+god, an easy answer - it's a hard path to trod and many who claim to trod it are really just treading water without really unlocking the full potential of what faith can bring to their understanding of the universe.
I suppose most of the above is rather generic, vague, and meaningless to anyone who has not really invested in faith. It's probably compelling to believers, and strangely alluring but not quite convincing to those on the cusp. All I can say to that is, that's faith for you. You can never accept faith on evidence; in fact proof actually denies faith (as Douglas Adams said, ironically given his own militant atheism!).
Look first, only to choose what direction you'll leap in. But then leap with all your heart.