Before you get all bent out of shape about how blog commenting is a horrible link building strategy, I want you to take a moment and approach this strategy with an open mind. What I'm talking about here is using blog commenting to build relationships and authority in your industry, and how those two things will ultimately lead to organic links and new traffic.
Forget Everything You've Read So Far
This approach to commenting is not about dofollow, nofollow, using keywords, or any of the other things you normally read about comments for links. We're not going to be searching for articles with great PageRank or lots of backlinks.
Finding the Right Blogs
When you're searching for places to comment, you're looking for blogs in your industry. And not just any blogs, but ones that receive some good traffic and engagement. They don't have to be the top blogs, mind you, but you want them to have some significant amount of active commenters already.
One great place to start is to PostRank. Look up your topic of interest, say SEO, and you'll find a list of some of the top blogs on that topic based on the amount of social shares and comments those blogs receive.
Another, for the Internet marketing industry at least, is Sphinn. Posts on their homepage are generally from blogs that have great content and therefore a good bit of discussion happening.
Once you've found a few great blogs to start with, then continue to branch out by following links from commenters to their blog. This will help you grow your base of sites to comment upon.
Also, on sites with many different authors, such as this one, check out the author bio to see if the writer's have their own blogs and join their community as well, assuming those are also in your industry.
Organizing Your Blogs
I'm a huge fan of RSS subscriptions via Google Reader for keeping track of the blogs in your industry. Since I have a number of different interests, I have them all in their own appropriate folders.
This way, you can easily see which categories have posts that have been updated recently, which will be important for the next step.
Try to be First
Don't do it in the annoying forum way by just commenting "first" or similarly, "great post." You want to be first, but only after you've read the article and know you have something great to say about it.
Just like the click-through rate on Google's first organic result is much higher than the following results, the likelihood of other commenters clicking your link if you're first is much higher than if you're getting to the party after 50 other people have arrived and left their mark. But even that is dependent upon the next step.
Only Comment if You Have Something Valuable to Add to the Discussion
This factor is huge! Kind of like the line you might have heard while growing up about how if you don't have something nice to say, don't say anything at all.
Well in this case, if you don't have something useful to contribute to the comments, don't try to comment. You will want to leave a comment that others can learn from and that the blog owner will be impressed by.
Become a Regular
Again, this goes against the link building grain of getting lots of links from lots of different domains. But we're not here to build links by spam commenting, right? Good, then that shouldn't matter.
You will want to become a regular face around the community. Which reminds me, if you don't have a Gravatar yet, then please do so. Or if the blog uses Disqus, sign up for a commenter account with them and get your profile photo up. Whatever commenting system the blog uses, make sure, if possible, it will have your photo associated with your comment.
This way the blog owner as well as others who frequently visit the blog comments will begin to recognize you and associate your valuable insights to your personal brand.
Go Above and Beyond
Don't just stop with your comment. Take that extra step to really get the blog owner's attention and tweet the post. If you took a closer look at my Google Reader, you will notice I did something a little different.
I renamed all of my subscriptions to the Twitter account for the blog. Why? Because while it's nice that many sites have social sharing buttons on each of their posts, not all do.
There's nothing more annoying than trying to find someone's Twitter handle when you're in a hurry to comment, tweet, and move on. So this way, I always have a quick reference point if the blog owner has neglected to make social sharing and connecting as easy as it should be.
A bonus point on this step - if the post is written by someone else than the blog owner, try to include their Twitter handle in the tweet as well.
This way you'll get appreciation from both the blog owner and the post writer, who is probably is owner of a blog themselves.
So you're probably thinking, that's a lot of time invested into commenting. What are the benefits?
When you start building great relationships from bloggers, then (assuming you have great content on your site that is relevant to them) they will start linking back to you casually in posts (much better than crappy, paid in-post links on irrelevant sites), retweeting your content, and start engaging on your site as well. Plus you will get traffic from the blog owner as well as other commenters who notice your responses and like them.
Of course, this is all if you have good content on your own site. If you don't have a blog, start one. And if you don't have great content, start developing it. Then you'll see a great trend in organic links and traffic from blog commenting.