The most efficient way to return a link to your site or blog is leaving comments.
However, the problem is when you leave comments on other blogs is that you actually create a feedback link to your profile, and if you have a WordPress blog, the link is connect with your name, Google does not value much, and often not at all.
So the correct way to leave comments, is to leave a longer comment, a few sentences. Leave at the end of the comment URL of your site or blog, it is as a kind of signature.
Often that will not be live links, and you will not be able to click on them, but Google will register them. And then, and it is not so important to be related blogs, because the link you post will be surrounded by content, and Google will register that as a kind of the articles and value your link more.
If you make such a back links to your blog or site, it's best to leave comments on various blogs, squidoo and huba pages, because Google just love them.
The best in this way of making back links to your site or blog is, those links are one-way links to your site or blog, and more value Google your site or blog, because many more links than you go to leave you.
Please note, if you have somewhere left a comment with a link, and author deleted that comment, do not leave that kind of comments any more on that blog. Some people do not like that, but I allow such comments, because I do the same.