Faith comes by hearing the word, but not to all who hear it.
Faith rarely springs up at 1st hearing, though it can happen.
A little seed planted, a little God, a little watering, a little God.. a response... All God.
I think that a combination of the hearing of the word combined with the work of the Holy spirit drawing us, but there is an unknown (to me) factor. I have to believe that all are drawn. God is not a respecter of men, and He wishes none to perish. I can't figure out why one person and not the other. He is blessing all equally, the rain, the sun, the nourishment, but ultimately only that which bears fruit is picked. Many are called but few are chosen.
There is free will involved. I know it makes sense to God, and if we were to be privy to His methods and the whole reality of it then we would be in awe. But from this side of Heaven, I cannot change my friends heart, I can only speak truth to him. We cannot force anyone to receive Christ, just as the Father will not force anyone to come, because it is a matter of the heart, not merely a verbal confession.
Ultimately I am left feeling so utterly insignificant and unable to do much at all to further God's kingdom. But then the Spirit says, "Some will listen. Some will come. You must plant where you cannot harvest and harvest where you did not plant. You must trust Jesus that He will not lose one of all of those that the Father has given to Him from before time and He is faithful to return them to the Father intact, but changed. Speak truth, speak life, love the unlovable, help the helpless."
So with the thought of the story of "Johnny Appleseed" in mind, and the faith that not all of the seeds that are planted will fail to grow, and the lack of knowledge of who it is that God is working on around me, I must give freely knowing it will not return void. Love selflessly, spend effort to help, be kind, be compassionate. Care about bout the lost and the saved.
Sometimes I just feel like a little lost kid with a bag of questionable seeds, and sometimes God shows me great trees in full bloom, bursting with fruit. Since in this arrangement we don't know who, we must attempt to share in some way with all.