How to engage your audience?

I will be spending time on writing a topic on "How to engage and attract your audience" post in my blog. I would like to have some advice from bloggers that are already successful in engaging with their audiences. With the help of the people in this forum and my research, I believe that we will be able to provide constructive value to people who have just started with no audiences.

As a starting point, look at competitors in your niche. More specifically look at their social properties (ie. facebook, twitter, youtube, etc) see which ones have "social signals" (shares, likes, +1). The more of these signals you see, the more engaged their audience is.

For example, lets say you were in the pet niche. Google "vetstreet" then go over to their website and check out their blog. You will quickly see which blog posts are the most engaging which should provide some value.

A simple free giveaway such as an ebook is enough to get comments and feedback. I have been doing this for years with a simple php script.