If you would like to know more about Dr. Cornelius Van Til, the father of presuppositional apologetics, you may find the following video useful. It contains the narration of a long letter written by Van Til to defend his belief in God, and more specifically the Christian faith. This is extremely thought provoking and insightful material, and even includes some interesting autobiographical information regarding Van Til's upbringing in Holland (you'll love his jokes about wooden shoes).
Here is a great example of Van Til's presuppositional method:
"... I propose to argue that unless God is back of everything you cannot find meaning in anything. I cannot even argue for belief in Him without already having taken Him for granted. And, similarly, I contend that you cannot argue against belief in Him unless you also first take Him for granted. Arguing about God's existence, I hold, is like arguing about air. You may affirm that air exists, and I that it does not, but as we debate the point we are both breathing air all the time."
- 2:43 on the video
I especially liked his critique of the presupposition behind rationalistic atheism:
"You have made the reach of your intellect the standard of what is possible or not possible. You have thereby virtually determined that you intend never to meet a fact that points to God. Facts, to be facts at all - facts, that is, with decent scientific and philosophic standing - must have your stamp instead of that of God upon them as their virtual creator."
- 44:30 on the video
Cornelius Van Til - "Why I Believe in God"
There is much more on Van Til here: www.VanTil.info