I was a drum major for two years at my high school. Loved doing it too. I didn`t have to do all the memorization of music, marching drills, etc. as the rest of the band. I played clarinet and sax too so...anyone can become one. And you don`t HAVE to be the top of your section, but it helps especially if you want to coach some of the other players when they have problems with the music. Some of the things that help in getting a drum major role:
being outgoing really helps
making a lot of friends in the band so that they respect you
willing to do the work that a drum major does
Drum major duties change from school to school but I enjoyed it all. And if you are the only guy drum major, the girls keep an eye on you more
(of course i mean to watch your tempo)