from: http://www.affiliateasshole.com/2009/08/13/building-back-links-with-blog-comments/

Benefits of Commenting

One good way to build back links is with blog comments.  Many Wordpress blogs have comments that do not have a nofollow tag.  Nofollow tags tell googlebot to not consider these true outbound links which means they will have no value towards building your Page Rank.  Commenting on other relevant blogs will not only add back links for your site but it will also bring traffic in.

Getting Traffic From Comments

When you add a comment to someone’s blog, they usually ask for name, email, and website.  When your comment is approved it will display with your name linked to your website.  Not everyone reads the comments, but the ones that do will spend more time reading onyour site.

Comments Are Like Search Engine Results

Comments at the top are more likely to be read than the ones at the bottom.  This is just like search engine results.  Search results on top are more likely to be clicked on than the ones on the bottom.  So you have to get in there early.  After you find a good block related to your niche, subscribe to their feed.  This ensures that right when they post it will show up in your RSS feed reader.  Make sure to comment as quickly as possible, but also make sure to write a good comment.

Writing A Good Comment

Writing a good comment takes some effort.  You have to actually read the article.  Do not just put a garbage comment.  Write something intelligent and thought provoking that actually adds to the conversation.  If you have a question about the post, write your comment and add the question at the end.  Make sure you enter a minimum of 3 sentences.  When I read blog posts I will only look at comments that are at least 3 lines.  Most comments under 3 lines are just kudos or garbage.

Finding Relevant Blogs

Here are a few sites that should help you find relevant blogs.

Google Blog Search is a great site to find blogs relating to your niche.  Enter a few keywords and click search blogs and a ton of blogs will show up.

Blog Catalog is another great site.  It ranks #1 for blog directory.  It will search their blog directory and blog posts for your keywords.

Wordpress.com is one of the world’s largest hosted blog solution.  These blogs are hosted on wordpress.com and not on independent sites.  It is still a good way to get traffic to your site.

Limit Your Comments

Try to limit the number of comments you do a day.  I would say 20 to 30 a day max.  Building links to fast may get you penalized with search engines.  Search engines know that people are trying to game them, so they will flag any activity that seems out of the ordinary.  Building 1000 back links a day with comment posts seems impossible.  Reading a blog post might take 5-10 minutes and there are not 5000 minutes in a day.