Hello David,
I know that this thread is a little old, but I believe your question is: important; relevant in our day; as well as extremely difficult and sensitive. Also, although I agree with much of the content in the replies, I didn't see alot of situational help in there. If you wouldn't mind, I'd like to weigh in on this.
First: the goal here is not to rid the world of a few more homosexuals. The goal is to see that everyone has an oportunity to hear, and see, the Gospel of Jesus Christ, and most importantly to come to a point of decision about Christ. I wrote this part to establish focus not because you don't already know it.
Second: most Christians will tell you that they are against homosexuality because the Bible says that it is inappropriate and abhorrent. I believe that the important part is not what Christians in general believe or what you believe; but rather, what the Bible indicates. Again, I'm sure that it is common knowledge that the Bible is our source of inspiration. What I suggest is that when the issue of homosexuality comes up in dealing with the homosexual, the response should never be a declaration of what you believe because they will argue with YOU. Instead, it should be a declaration of what the Bible indicates because they already know they can't argue with GOD (unless they want a smack). The idea here is to set aside the specific issue of homosexuality in lieu of the broader issue of sin in general, and Christ's forgiveness for those who will believe in Him and follow Him. In the past, I have had lengthy discussions with homosexuals about Christianity. The trick is to be nonconfrontational about the issue yet uncompromising about Biblical standard. It isn't easy. When in doubt, I would say something like, "Well, this is what my Bible says and I'm just followin' this Jesus guy." Crouch behind the Bible and let their bullets bounce off of it, metaphorically speaking.
For everything else, not concerning the issue of homosexuality, I would let them see that being a Christian works and how it works in your life, showing compassion, overcoming evil with good. However, do not ever ever ever lie about what you believe; they are watching for it; they'll see it coming a mile out, and it will ruin everything. If your friends are still your friends after having learned that you are a Christian, then I think you have an opportunity to share Christ. Just don't forget your shield: the Bible.
Please excuse me; I see things in the martial, in terms of war. Homosexuality as a concept has become a choke point with a high stone wall set against us in our efforts to spread the Gospel, a wall of politics and social mores. Such walls cannot be broken down with a frontal assault. I propose that we must tunnel under their defenses to pop up inside their stronghold with Bible in hand, a loving smile, and "Jesus Saves" painted across our chests. The rich man in the parable with Lazarus found himself in hell and tormented. whether you think the parable is true or just a story, at the time of Jesus' oration there were men like that rich man tormented in hell. In the last 2000 years their situation hasn't changed. Whether a man's sin be homosexuality, or murder, or adultry; How much is too much effort to keep them from burning for the next 2000 years? Sometimes the war for souls is difficult and uncomfortable. Who really is not worth the effort?
At least, this is how I see it.