For just one moment imagine yourself anywhere in the World were you could be completely understood by another person who may not speak your tongue, but for just that moment, he could understand your faith. How would you defend your faith in Jesus Christ? The World is a diverse and intricate place full of many different religions. 
Over 33% of the population is considered Christian, which includes Catholic, Protestant, Eastern Orthodox, Pentecostal, Anglican and the like. The fastest growing religion today is Islam then followed by 16%, which is "non-religious". That being said, over 33% of the World believes in Jesus Christ. Of course, even in this category, some are false teachers in saying that He is not the only way. So let's take Islam, for example. In their sacred text, the Quran,they believe in Jesus as a prophet of God. As a matter of fact, they believe that He was born a virgin birth and that He was the God's greatest messenger to mankind. However they do not believe that he was crucified, instead they believe that Judas took his place and that Jesus was somehow met up in the clouds, as they do not believe God will allow this fate to happen to his messenger.
So where do we start from there? Do you reject their faith and immediately turn them off? What would Jesus do? Instead, ask, what DID Jesus do. I would show them who Jesus is in my life and how I have made him Lord over my life. I would give them a glass of cold water and be a neighbor and friend to them. I would allow the Holy Spirit, who dwells in me (thanks to the crucifixion) and is working through me in order to show a Muslim God's eternal and everlasting love. Next I would ask about their faith and build a relationship with them. Once trust is established I would ask if we could debate the merits of our faith.
For instance, by their very sacred document, the Quran, they state that Jesus was a prophet and perhaps God's greatest messenger to mankind. There you go, that is the turning point right there. Simply put, by their own document, you can challenge and refute their claim. Why? How do you ask? Simple. Either Jesus was and who He says He was OR He (Jesus) was a quack and a liar. I am not saying anything to the contrary. Jesus is Messiah. Jesus is our Savior. Jesus is the only way. Over 300 Bible Prophesies have been fulfilled by Jesus. Therefore, you cannot say in the Quran that Jesus was a great man only to denounce his testimony. Jesus foretold of his death and resurrection. Jesus was crucified and on the 3rd day He rose again. If you confess your sins to him and admit that you are a sinner and you believe on Him that he was born a virgin, died on the cross and rose again on the 3rd day and you confess your sins to Him and believe - YOU WILL BE SAVED.
Simply put, you cannot say that Jesus was a great prophet and a Messenger of God, only to denounce Jesus's own testimony of truth. Either he was he he says he was and we believe or you completely discount and reject him. But remember, at Judgement, every knee will bow and every tongue will confess. Confess what? Simply put, "Jesus is Lord & Messiah! AMEN!
Dante