Build Backlinks by Commenting on Blogs
Commenting on blogs is a lot like forum marketing using signatures. Like that method, it can be overdone. So please don't go crazy with it. And don't write meaningless, spammy comments for the sole purpose of getting a link back. It will annoy the blog owners, and could well result in your own URL being penalized in the long run.
Of course dofollow blogs are more effective for SEO if you use this method. But the "nofollow" blogs are still worth contributing to. There is some evidence that while Google doesn't give you SEO benefit for commenting on them, other search engines still do. Anyway, if it's a high traffic blog, you'll get some click-throughs coming off your comment.
But in my opinion the greatest benefits are indirect. If your comments are interesting and thoughtful the owner of the blog will probably have a gander at yours. If he likes what he sees he may reward you with a link back in the body of a post at some stage. Also, a lot of the readers of blogs are bloggers themselves, so one of these guys might link to your content, too.
Comments that you write on other people's blogs often result in reciprocal ones on yours. These also bring benefits SEO-wise. This is because Google indexes this content, as well as the blog post itself. So if these contributions keep growing, this is a plus in the search engine's estimation of your blog's value. It's another sign of its "pulse".
The other benefit of commenting on blogs, much like participating in forums, is that you are honing your ideas and developing more content. You can always collate your contributions on a certain theme and then post them to your own blog, site or article directories. For these reasons alone, blog commenting is a great free strategy.
So, just try a few searches for blogs in your niche, and once you've found some, add some good opinions. You'll find that this can be a self perpetuating process, because good blogs attract other good bloggers who like to comment. Sometimes, you can find dozens of other good blogs via the thread below just one popular and insightful post!
If you are keen to find dofollow blogs in particular, it's pretty straightforward. Do a search for a chosen keyword plus "dofollow" and you'll find lots of individual blogs popping up. There are also lots of lists of such blogs posted on blogs and forums.
Since bloggers often announce their decision to remove the nofollow tag, you can also search for your keyword with the phrase "now dofollow". That will turn up a surprising number of blogs, too.
Another trick is to forget about "dofollow" and search for the keywords "commentluv" and "keywordluv". These are very popular plugins designed to reward commentators. Bloggers who have installed these often have dofollow blogs.
Needless to say, when you find and comment on these blogs, make sure your comments are thoughtful, relevant, polite and contribute to the conversation in some way. And while they don't have to be epics, try and add a few lines of text at least.