I grew up in a fundamentalist Christian household. As I entered my early teens, I realized that I wanted to pursue a career in the life sciences, and being a strong extrovert, I let everyone around me know what I wanted to do, including those in our church. So, the church leaders started giving me books, videos, and pamphlets from various young-earth creationist organizations. Also, even though I was in the AP science program in high school, they never touched evolution--too controversial for a small midwestern rural community.
So by the time I went to college, I was immersed in YEC and rather ignorant in evolution. I didn't quite buy the whole young-earth stuff; it just didn't seem plausible to me. But I did have some pretty negative views about evolution. In my second semester as an undergraduate I took an evolutionary biology course, which was given by a professor who turned out to be my major professor in graduate school. He was very gruff, direct, and had no patience for creationism. Nevertheless, I approached him after about a week of class and told him my history and that I had some questions about some of the creationist arguments I had read.
He peered up from his typewriter (yes, he still used a typewriter), looked at me, and asked "Do you want to be a scientist?" I replied that I did, and he answered, "Then you need to learn to think like one." He then asked me what I thought was the most compelling argument the creationists had put forth. I answered that all the quotes from various scientists regarding the lack of transitional fossils really struck me as important. He instructed me to take a list of those quotes and arguments and go down to the library and look up every one of the original articles and read through them completely.
Well, it took me all of about 2 days to realize the extreme dishonesty that is at the core of YEC, and completely disavow everything to do with it. I was so appalled and disgusted that people claiming to be "Christians" and "on the side of God" were so blatently and pathologically lying, time and time again, I really didn't know what to do. The quote mining was so egregious, it made my stomach turn.
When I reported back to my professor, he wouldn't let me off the hook. He gave me a list of more papers to read that described transitional specimens in detail. While rejecting creationism was a very quick process, it was over a bit more time that I started to realize just how well evidenced evolution and common descent are.
And my professor absolutely made his point; when in doubt, look at the data. To this day, my mantra is always, "LOOK AT THE DATA!!"