Most everything I could say has already been covered but I'll add my bit anyways
I've been drawing comics and putting them online since (roughly) 2008 and it's only been this last year that I had a really significant increase in followers. I started posting more than I had been before in 2012 and in 2013 even more (and to a schedule), so there's probably a connection there. Before then updates were very sporadic, 7 month intervals don't really work well for gag-a-day comics haha. My main intention when I started making comics was just because I wanted to make comics/tell a story/joke. I wanted people to read them of course but it was (and still is) mainly an act of love (I may be wording that weird...).
Treat your followers well, if you have time try to reply to comments and answer questions. Be careful not to get taken advantage of (some people will ask unreasonable things) but show people you're not ignoring them.
Take advantage of social networking. I've found Tumblr to be really good. Not everyone subscribes to RSS feeds (if you have your own site for your comic) so making use of social sites like facebook or twitter are a good way of giving people an easy way to follow your comic.
There's no one way of gaining a following, what works for one person may not for another. The main thing, in my opinion, is just to keep doing what you're doing as long as you love doing it. Patience is very much a virtue and it will, most likely, pay off.
:¬)