Hi! Do you like to listen to ALL kinds/genres of music? Do you have a huge MP3 library - do you own 100s and 100s of songs that you listen to? I think that knowing what song best fits what movie/score/scene means that you should know as many songs in all genres as possible.
For example, if I told you that I am making a movie and am looking for a classic love song from the '40s, would you know what to recommend? You must know more than just current music.
That's just the beginning! We lived in LA for a while and learned that it is ALL about connections - relationships, people that you meet and know. So learning as much as you can about all kinds of music is the first step. Then, making the right connections to be hired is next. If you don't live in LA or NY, it may be more difficult.
But if you really want to do this, then give it your all. Also, know about movies from all decades, not just current.
All the best!