Often inbound marketers look at numbers and analyze traffic, leads and the like. Sometimes blog subscribers is an overlooked area. I must admit there are probably some areas where we could improve in this area. We do however try to use "subscription forms" on all or at least the most popular pages of our site.
Blog subscribers seem to be a little slower in growth, that is unless you are creating remarkable content. So the first place to start would be in the quality of content. If you already have a "subscription form" on all pages of your site congratulations. If you don't start adding them today!
Other ideas are to create a Blog Subscription landing page that is focused only on attracting more blog subscribers. Then once you have this page you will need to start promoting this landing page. This can be done in email signatures, in e-newsletters, through PPC or why not add a Call To Action button at the end of each blog article as a reminder to your readers.
Other options could be sharing the idea through presentations on the last contact us slide. You might also try to create some videos that show the importance of getting free content from you and how to subscribe.
Try a few of these ideas and let us know how it works out for you. If you have other ideas, please feel free to share them in the comments section below. Thanks and happy blogging!