Link other comics, from your front page. Lots of comic creators check their referrals obsessively, and check out comics that have linked them. That's how I got noticed and linked by
Saturnalia and
Spikey Haired Dragon, Worthless Knight.
Be active in forums, with a good-looking banner link to your comic in your signature. Be an appealing person on those forums, astound them with your wit and artisticness.
Join some webcomic communities. Small close-knit growing ones are especially good. I had my comic,
Evilish, join
Pens and Tales. (it's not accepting new members right now, but it's an example. Join some listings too, like
Belfry,
OnlineComics.net, and
The Webcomic List.
Do some guest comics for popular comics (when they say they need them or say they're going to stop updating for a little while). I got a bunch of new readers after doing a guest comic for
VG Cats.
Do some link exchanges, but try not to link more than just comics that you think are interesting, or you'll get less attention from referral hits
Do fanart for other people's comics. If they like your art, they'll take note of your comic, and will either link you back or do fanart for you in return, or both.
Make friends with other people who make webcomics. You'll not only get interesting and in-common friendships and links, but you'll probably get fanart and other comic-related favors. I made friends with the creators of
Treasure Hunters (which is how I was invited to join
Pens and Tales),
Firefly Cross,
Red All Over,
Sticky Evil,
Saturnalia,
Deity Permit, and
Heaven's Assassin. They're all amazing and interesting people and I love them so much.
heart heart I'm glad I have a comic, because with it I had something in common with them to jump start our friendships.