Let there be no compulsion in religion: Truth stands out clear from Error: whoever rejects evil and believes in God hath grasped the most trustworthy hand-hold, that never breaks. And God heareth and knoweth all things.
(Quran : 2.256)
Say thou: "This is my way: I do invite unto God,- on evidence clear as the seeing with one's eyes,- I and whoever follows me. Glory to God! and never will I join gods with God!"
(Quran : 12.108)
Invite to the Way of thy Lord with wisdom and beautiful preaching; and argue with them in ways that are best and most gracious: for thy Lord knoweth best, who have strayed from His Path, and who receive guidance.
(Quran : 16.125)
Never force Islam on the people. Instead let the truth stand clearly. Present your evidence and respect a person's right to believe and disbelieve.
Call unto ALLAH is more important than calling to Quran alone. Do not emphasise Quran alone more than Islam.
Provide evidence clearly so as the person you speak to can actually 'see it'. Unclear evidence may actually turn people away from Islam itself.
Invite to God's way.
Invite with Wisdom and Beautiful Preaching.
Argue with them in the ways which are best and most gracious.