When you are posting a comment,  you can use name as the hyperlink or Include a back link to your site either down the bottom of the blog comment.

You need to make genuine comments, if no, your commets will be get deleted by that dofollow blog. and do not include too many links in the comment, it will be seems for spamer.

Place your  comments on dofollow blogs that are relevant to your site.

Try to use keyword for your anchor text of the links to targeted to the page you are linking to.

And, it the page of  dofollow blog have many comments on them, then, do not  leave your comment  there, Just for new page or post, The higher up on the page that your comment appears, the more value you will get from it.

And bear in mind that many blog comments are moderated. Your comment may not appear on the site until the site owner approves it. Then, you will get more free backlink.