In short, commenting will not help you. It may drive a few hits here and there to your site, but search engines will not consider those links as authoritative links.

Nearly all links on blogs within the comments are nofollowed to help with moderation of the web as a whole.

if you have something valuable to say on a post, you ought to leave a comment -- but do not go around from blog to blog leaving worthless comments as it is just a waste of your time.

Say something of value and if other people also see it as valuable, they are likely to read your blog and link to you with a real link.

Quality over quantity.

If you comment on dofollow blog , then search engine will consider as authoritative links. You can find lot of dofollow blogs on internet using normal search engines or special dofollow blog finding software.

I am agree with shansilva .. but don't spam otherwise moderator will lock you

Commenting on blogs is a great way to receive traffic.If you are just using it to post a link and not adding value to the conversation, few people will likely let you comment, or won't approve them. So,be sure you give a good commnet.

commenting is the one of the way to get traffic but it takes time to get traffic in this method.

Commenting can help somewhat if it dofollow links but you should not depend only on this.

ya i agree with you only blog commenting will not help. Blog commenting with other off page techniques will give good results.

Google likes natural backlinks. That's really all they say. A backlink from a blog is more natural when it is in the comment section and not the name section.

If you comment on do follow blog/site , then Google will consider as a regular link.Otherwise there is no use....

But comments is an indication of the popularity of the site content.