You have been doing it all wrong according to WikiHow:
http://www.wikihow.com/Persuade-an-Atheist-to-Become-Christian
According to Wiki, since when have you followed or listened to the advice of Wiki?
True believers do not Persuade, coax or cajole.
It is misleading to think that befriending, helping or even the way we treat and talk to others will lead them to God.
Romans 16:18King James Version (KJV)
18 For they that are such serve not our Lord Jesus Christ, but their own belly; and by good words and fair speeches deceive the hearts of the simple.
The truth is that the Truth about Jesus Christ stands on it's own.
Truth faith comes by hearing the word and believing.
King James Bible
So then faith cometh by hearing, and hearing by the word of God.
People are often lead to the LORD, by the Christian living their lives with God in Christ.
If your relationship is a true relationship with God. Then you can only pray others will come to find God, too.
A person may ask you about your faith and you can share it. But no one can persuade, Coax or cajole someone to believe
in Jesus Christ and God.
It has to be their own way through Christ.