Take a brief look at the comments that are shot before yours. Notice the names they are using for commenting. Are they using their real name or a pen name? If they are using their real name, so should you. If not, then try to use your targeted keyword instead of the real name. The URL you entered will be incorporated with your name. So using a keyword will boost your ranking.
Below are a few working guidelines that you can follow while commenting on blogs:
1. Comment on relevant niche blogs to yours. Because, the weight age is more if you get links back from relevant sites than non-relevant ones.
2. Make an useful comment that will be helpful to others. No one likes to see/approve “superb blog” or “thanks for sharing” or “see my blog” in the comments section.
3. Comment only when you can add some more useful information to the topic discussed in the post/previous comments else go for another one.
4. Use deep linking of posts in comments. That means if you have written a similar post on your own blog that is relevant to this, then point back to that post. It is easier for the search engines to crawl your blog and it also makes the readers to read your version too.
There are few people who only comment on “do-follow blogs”. But, I suggest you to comment on all blogs that are relevant to yours. May that be a do follow blog or a no-follow blog.