If you want to increase traffic then don't listen to anyone who professes there are passive ways of doing that. Increasing traffic to a blog is hard work. If you want your blog to rank well in search engine results then that begins with creating and publishing original content ie. unique content that cannot be found anywhere else on the internet.
See How to Identify Your Blog’s Target Audience http://onecoolsitebloggingtips.com/2013/09/01/how-to-identify-your-blogs-target-audience/
Two ways of attracting like-minded subscribers are (1) commenting meaningfully and frequently on blogs with similar content and (2) being active on social networking sites.
On the bottom of your Admin page you will find a link to the Learn WordPress.com blogging Tutorial prepared by Staff. http://learn.wordpress.com/
The support documentation is all found at the Support link http://en.support.wordpress.com which is also on the bottom of your Admin page.
These 5 videos introduce how Google discovers, crawls, indexes your site’s pages, and how Google displays them in search results. It also touches lightly upon challenges webmasters and search engines face, such as duplicate content http://onecoolsitebloggingtips.com/2010/03/22/5google-webmasters-video-tutorials/
If you are using a WordPress.com theme good SEO is a given. However, going beyond the theme what the blogger has done within that structure is worth evaluating. Whether you write informative, persuasive or controversial content learning how search engines work, and how to apply basic SEO to you content will benefit your blog as it will increase traffic from targeted readers. http://onecoolsitebloggingtips.com/2011/10/21/two-seo-videos-for-bloggers/
6 Ways to Make Google Your Blog’s Best Friend > http://onecoolsitebloggingtips.com/2012/10/08/6-ways-to-make-google-your-blogs-best-friend/
Here are 25 basic steps to take to increase traffic to your blog: