Your goal of your blog should be to provide useful information to the reader. You want to be answering the questions they have on a specific niche. So, the question is, how do you find out the questions that people are asking? It's simple - get a Contact form! I love when people ask me stuff. I readily respond and I feel like my readers love specific examples.
Nothing can be communicated more vivdly than that of personal experience or interest. As in songwriting, if you write about things you don't know about, you're going to end up with a hell of a mess. To learn different things to have more topics to write about - READ.
I think if you are taking blogging seriously, every blog should have a "contact me" section. Honestly, I hate when I do need to contact another blogger and they never have their info for me to do that!
Yeah i think contact info/section, not just on a blog but on lots of other types of sites is very important.
Another way to find about questions will be monitoring niche forums and discussion sites like Yahoo Answers and Google Groups.