I am a young-earth creationist because I believe this is what the bible teaches. Because of this, I am a big supporter of Answers in Genesis.
Dr. Jason Lisle, of AiG, has written a book that I enjoyed very much and found very helpful. The text, entitled The Ultimate Proof of Creation, is an apologetic work that focuses on why a young-earth creation position is the only reasonable and logical position to hold. Lisle debunks both atheistic/materialistic/evolutionary positions and various Christian positions that do not believe in a literal interpretation of Genesis 1-2, such as theistic evolution.
Three aspects of this book stood out to me as memorable:
First, Lisle proposes that "the ultimate proof of creation is that if biblical creation were not true, we could not know anything." I found his thesis to be convincing. I'll let you read the book to find out more about it.
Second, Lisle suggests a two-fold strategy, based on Proverbs 26:4-5, for answering people who hold to unbiblical presuppositions. As creationists, we are not to agree with the faulty assumptions of those who are unscriptural, but are to show the illogical endpoints that their assumptions would lead to.
Third, Lisle states that when giving a reason for the faith, there are basically two positions: the "evidence first" approach and the "bible first" approach. The author indicates that we must take a "bible first" approach. If we set the bible to the side, we give up our primary evidence for a young earth.
It is this last point that has had the most impact on me. In the past, I have had a tendency to argue for God's existence and God's creation from the scientific evidence. Quite simply, I left out the bible. From now on, I'm going to speak from the bible first when discussing the existence of God and a literal young earth creation. Of course, I'll mention scientific evidence, but the bible will come first.
The reason for this, as Lisle states, is that the bible is the only objective source of information we have. All scientific evidence can be interpreted in multiple ways. While the bible is absolute, scientific evidence is relative.
Even if you don't plan to buy this book, it is fun to read a few of the reviews on Amazon.com. Not surprisingly, the book was either reviewed very favorably or very negatively. It all depends on the worldview the person has.