Advertising here on the forums is best done by linking your comic/talking about it in the relevant threads - like "How did you come up with your comic name?" or "Post your latest page!" or story-specific threads that are asking about people's comics in general, or asking you to share specific experiences in creating your comic. There, it's alright to link, because it's relevant to the topic.
Just don't go into threads that AREN'T relevant and spam links to your comic, and I think you'll be alright. "Do you read finished webcomics?" is a thread where you shouldn't link your own, for example - same with "Do you look at older pages or newest ones?"; they're general questions about webcomics culture, and not about the making of webcomics.
Outside of that... social media accounts are a good idea, as long as you don't spam too much. I tweet my updates, and link to them on my Tumblr, and people seem to be perfectly fine with that.
