one of the big theories is the GAP theory, I can remember like it was yesterday when I first heard about it, It answer so many questions I had about dinosaurs, all the scientists saying the earth is old etc etc. I could finally answer my friends questions when they asked. And without really studying it, I took it, and ran with it, for years I defended it.
then about ten years ago I started to study about the flood. I love to read, so started to read book from people and studying all views, And this is what changed my view, and led me to become a YEC proponent.