Both @josef_yi and @respheal have the right of it. As for what you can do outside of that?
We go to conventions and table there. For the past two years we've tabled at cons with the sole purpose of telling people about our comic and getting them to read it. We sell prints, and network with other artists. Additionally we present panels on creating webcomics, working with creative collaborative teams, and character design, world building etc. This gives folks an understanding that a. we know what we're talking about and b. gives us to use our comic as examples and case studies we present. For example, in the character design presentation we go through a bunch of information, and then end the presentation with a case study from a character we really struggled to nail down. The team talks about how we used the principles we presented to finalize that character into a great design.
Now we usually don't go to cons expecting to make table back, because that wasn't what our purpose was for. When you're promoting your return investment is new readership - this is especially true when you're just starting. We saved on costs by attending tiny local cons ($50 for a table), or splitting tables with friends. It's not an avenue that everyone can do, but it's what's really helped us out.
Also, forreal, get on twitter and start getting active in the comics community there. <3
