Blog comments are a wonderful way to get free links to your blog and work wonders when your blog is new. When the blog ages quite a bit, the daily traffic levels will be higher, so it will be harder to see the traffic coming from the comments themselves. In order to be effective for promotion purposes, blog comments need to be: on related niche blogs, valuable, timely and consistent with the URL naming convention. An important thing to remember is to reply to comments left on your blog, as this is polite blog etiquette.
Finding Related Blogs to Post Comments
This is the most time consuming step, as before you can leave comments on other blogs, you need to find other blogs to comment on. It doesn't have to be hard; a Google blog search can do most of the work for you. Once you've compiled a list of blogs in your niche, you'll want to take the time to look at each one closely, because you won't be able to comment on them all each day.
Choose 5 blogs to comment on regularly, and keep 5 to 10 more on reserve in case the first 5 don't have any new posts or become unavailable for some reason. Consider how many people are already commenting on the blogs, how well known the blog is and whether or not they use "do-follow."
Do-follow is a link attribute that allows Google to count the link to your blog as a backlink, therefore increasing the search engine ranking. However, many blogs elect to use the "no-follow" attribute as a result of spammers leaving useless comments crammed full of keywords.
Comments Must Be Valuable
As a result of spammers, there are many comment spam plug-ins and features to stop those kinds of comments from coming in. This is why it is very important for any comments you leave to be valuable to the blog. Really read the post you are commenting on, and offer something to say about it specifically, rather than using a generic blog comment such as "Nice Post! Come check out my blog."
Comments Must Be Timely
Comment on recent posts, rather than older ones, to increase visibility. While older posts may get visitors, they are much less likely to be seen than newer posts. Try to keep your comments to a post that was written within the last week (or the most current post on the blog).
Comments Should Be Consistent
When commenting on other blogs to help build links and traffic to your own, use the same name and URL each time. If the first blog comment uses "http://blogurl.com" all comments should follow that, because search engines will see "blogurl.com" as a completely different website.
Comments can help boost the search engine rankings of your blog, and comments should always be valuable to increase the chance the blog owner will post them, adding to the community and visibility of your blog for readership.
Valuable insight, timely comments and consistency will help build your credibility within your the niche community. This will help you distinguish yourself as a person who's blog is worthy to be read versus a spammer.