I don't have many followers, but this is from other people's experience as well as mine. Writing plenty of good hubs always helps.
Commenting on other people's hubs is also very useful.
If you really enjoyed a hub, share it on hubpages and/or social media and mention that you did so in your comment.
Answering questions and participating in forums (which I don't do much) also gets you known to others with similar interests.
If you publically appreciate someone's work or get into a conversation with them in the comments, and are following them, or then follow them, then that person is likely to follow you back.
Following 100's of people will get you an unbalanced following/follower ratio, like 1,2000 following and 62 followers, and that itself is a turn-off for me and perhaps others.
People like to be followed as individuals, not as part of a list.