Well, I find that if I post every day, that helps a lot! Also, I make it a point to go around and comment on peoples' posts. People already on my followers list of course, but ALSO I go into the 'new posts' section, and pick random people who's posts interest me and comment there as well. I find that generally people, when seeing a new face commenting on their posts, will check out their profile and start commenting in return, many times following. :)