I was reading this article on linkedin and thought it was very well put:
"10 Social Media Tips for Authors"
http://rdd.me/nggecu3t
Particularly relevant to travel bloggers:
Act like NPR
NPR provides great content 365 days a year. A few days a year it runs pledge drives. No one I know likes the pledge drives, but we tolerate them — and some of us even give money. Why? Because NPR has earned the right to promote its pledge drives by providing such great content. This is a good model for authors too: Provide such great content that you can promote your book when it’s done. If you do this very well, people may want to reciprocate for the value you’ve added to their lives by buying your book. So just imagine you are the producer of “Fresh Air” or “All Things Considered” and look for interesting content.