Good tip and it is also a good idea if you are making blog comments on articles in high ranking sites to make sure that the comment is useful and relevant to the post otherwise the webmaster may just delete it,
Blog commenting is helpful if you post relevant posts. Links lose value if it comes in a huge number from same domain. So diversify, interact ans post original comments to get quality links form blog commenting.
Choose your niche related blog to have maximum benefit. Leave valuable comments which adds information for the visitors. Comment both on do-follow and no-follow blogs.
Commenting on blogs is a good way to get backinks for your site. Your comments should be informative and useful and not driven just by the desire to get backlinks. They should generally be made on blogs in your niche. Where allowed include your signature.
Blog commenting is a very good way for promoting a website but commenting in an irrelevant blog is nothing but simply wasting your time.
Blog commenting may sure give us positive impact but for this we have to search Do Follow blogs. I know it is very hard to search but we will get maximum of our work if we have Do Follow back links.