Blogs are liked by the search engines and they are visited by the search engine spiders frequently. These blogs are also indexed frequently by these search engines in their databases. The search engine spiders also visit the links on the blogs, if they are permitted by blogs, at the same time.
Hence, first find a blog that has a similar theme as your own website and has a better ranking in the search engines, preferably in the first 2 or 3 pages of the search engine result pages.
By commenting on such blogs with a reference to your website using a link, the search engines can also visit and index your web page frequently. Apart from this, your comment will also get a much needed back link from the blog. If the blog is popular, then the visitors that visit the blog will also follow the link that you have placed there and visit your site.
You must take care that your write a good, interesting, and descriptive relevant comment so that the comment is not deleted by the blog site.
Instead of writing a short comment that just says, “Thank you”, etc., write a useful comment to get noticed by other visitors. Even if the search engine spiders do not visit your website from the blogs, the visitors will surely visit your website if your comments are interesting. This is the major advantage of driving web traffic to your site. So, find such blogs that are relevant to your website’s theme, and generate plenty of targeted web traffic to your own website.

Blog comments are invaluable. They're great backlinks, wonderful for SEO purposes when blogs are kept as follow-links, and people tend to follow them on their own, so it's new visitors all the time.

Writing relevant comments on other blogs are a good and free way to get some back links for your site. Just be sure to write relevant comments otherwise they would get deleted. Always look for the dofollow tags to get a good back link.

Nod. I've even considered starting a few of my own blogs on various blog hosts to build up relevant backlinks.

Another way to write some useful comment is to find blog post that has the same article like yours and suggest your url. This is a sure to get your comment approve and to get some free traffic as well.