Join online forums related to non-musical subjects. Identify a subject or topic that has cross-over appeal with your music. For example, Alice Cooper claims that his music has always appealed to fans of horror films. Once you identify a topic, sign-up to online communities related to that forum. Don't "spam" the boards by constantly promoting your band. Contribute, make friends and then start a thread about music. This gives you an opportunity to mention your act. Choose forums with lots of users, but not so many that your thread gets buried in a few hours. Look for sites where the threads have around 40 to 50 responses per day.
Sign up to a free mailing service, such as Your Mailing List Provider or Bravenet. Enter you contact details and website details, when prompted by the site you choose. Highlight the code for the mailing list sign up box and paste it into the HTML editor on your band's website, so people can sign up when they visit. Send out an email each week and offer incentives for any recipient that signs up a friend. For example, send an unreleased MP3 to the first 100 people who sign up a friend.
Perform out of town shows. Put up posters in colleges and music stores in the nearest town to your home town, requesting a gig-swap. Include a link to your website so people can check out your music. A gig-swap is a reciprocal arrangement between two bands. Book a gig in your town, so they can open and then they return the favor at a gig in their home town. Both bands get to play to a ready-made, new audience.
Sign up to all well-known social media platforms, such as Youtube, Twitter and Facebook. Use your band or artist name if it is available. If it's taken use a take on the name. For example, if "Twitter.com/JackBrown" is taken, use "Twitter.com/JBrownMusic" instead. Update your profile at least once a week, even if you have nothing to say. If there's no news from your band, post a video of another band that you like. While this may divert the attention away from your band momentarily, it's important to keep your name at the forefront of people's mind, especially in the social media context. The other band may return the favor and send of their fans your way. Encourage friends and fans to share your music.