Listening? Sure! Listen to what people are talking about and more importantly what help they are requesting on Twitter and FaceBook. If it's something in your area of expertise – answer their questions.
What does this do for you? It sets you apart – first as an expert in your field and second as someone who cares and wants to get involved in the conversation and the community.
Do you always have to put a link back to your site? A huge NO! By answering questions you are perceived as an expert and people will want to see who you are. Plus you are tweeting and facebooking regularly, aren't you? If you are, those are the posts where you promote by giving a link to your site. People who want to find out more about you will do the one extra click it takes to find your profile. Of course, this only works if your profile is complete. It is, isn't it?
Cathy Perkins, The WordPress Wizard