Kiwi this is a great topic and I love the responses.
I agree with Kittn1, it's hard to beat the Romans Road, that is a great method.

Over the years I have developed another method that seems to produce very good results also...

One day a shaft of light hit my brain and I learned from the Bible that Jesus liked to reach people with unusual questions.

I usually go from John 3, to Genesis, then Romans and Revelation. These passages are linked in my Bible, so I flip right to them with no stumbling or hesitation, it's all pretty quick...

I always start by asking them the same question:

"Do you know the one thing Jesus said you MUST do
in order to enter the kingdom of God?"

This question always seems to make them think, sometimes they will say join the church, or be baptized, etc... and then I take them to John 3:1-7, and show them the answer.

From there I focus on the BLOOD ATONEMENT, and continue with unusual questions:

Do you remember the names of the first man and woman?
They always answer, "Sure that was Adam and Eve."
Yes, and after they sinned what did they wear?
They always answer "fig leaves!"
Yes, and did you ever notice God replaced those fig leaves with something else? Not as many people know this, so now I have their attention...

Then I take them to Genesis 3:21 and show them the first blood shed to cover man's sins. I try to explain the trail of blood all through the Old Testament, and then how God himself shed His own blood for them (Acts 20:28). I have found there is amazing power when witnessing about the blood of Christ, it's strange and the Holy Spirit seems to really bless this, I can't explain it. A quick stop off at Ephesians 2:8-9 shows them they cannot earn this gift, but they must accept it. Then to Romans 10 for what I believe may be the most powerful verses in the New Testament:

8 But what saith it? The word is nigh thee, even in thy mouth, and in thy heart: that is, the word of faith, which we preach;

9 That if thou shalt confess with thy mouth the Lord Jesus, and shalt believe in thine heart that God hath raised him from the dead, thou shalt be saved.

10 For with the heart man believeth unto righteousness; and with the mouth confession is made unto salvation.

Now the trouble starts...
At this point, the dog will start barking, the kids will start screaming, the phone rings, etc. it never fails. I always have used a pertner to "control" these distractions, and I will look the man straight in the eye and tell him to ignore it because someone is trying to distract him at this very moment, because his eternal soul is in the balance. So we are able to even use the distractions against the adversary to strengthen the witness for Christ. I have seen grown men break down in tears under the conviction of that old King James Bible, and I can tell you this: at this point if he wants to be saved, there isn't one thing in the universe that will keep him from it!

At this point I can tell if they are ready...

and if they are, I show them Rev. 3:20:

"Behold, I stand at the door, and knock: if any man hear my voice, and open the door, I will come in to him, and will sup with him, and he with me."

Then I ask them straight up, can you think of any reason why you wouldn't want to open the door of your heart RIGHT NOW, and invite Christ in your life? I would say over the years we have seen a success rate higher than 90 percent with this method, where they will bow their heads at that moment and pray for salvation.