I always post about my comic there on update days, and sometimes participate in things like #webcomicchat, although I don't find it terribly effective....mostly I use it to talk to other pros, reviewers, and publishers. Once they're familiar with my work, especially my print work, I tend to get retweets and shares out of it.
But mostly I like twitter for the slow build up of friends and connections, and thus my own reputation. Being on it for some years means there's always new cartoonists and fans to meet at conventions. I also use it as my primary news source, although this kinda sticks me in an echo chamber!
