I definitely agree with getting experience--paid or unpaid. I worked at a library for almost a year before deciding to go to library school, because I wanted to test out the field before investing that kind of time and money into it. I found that with most of my classes, my experience working at a library helped me to do well in the class. That being said, I went into cataloging, which was something I could only learn in a classroom setting. (Working at a branch library meant we were isolated from most of the technical processing, so even if you wanted to learn, you couldn't...) I would also see if you can spend time with librarians in different fields to see what they like about theirs.