The comments which you are going to post for generating backlinks must be having relation with blog post niche and it should never look like as just promotion of your website. For an example, if the blog in question deals with art galleries in the greater Sydney area then you should never share your personal experiences which you had when you visited that location. Perhaps you should focus on writing more about quality of the pictures and arts. You should not place comment which looks like spam because blog owner may view it as spam and your comments will be banned or removed immediately and as a result your website's credibility will go down the tubes.
What is the reason behind popularity of Do-Follow Blogs?
A blog's do-follow attribute grants the blog's "link juice" to pass on to the websites from which commenting has been done. For any website Do-follow blogs are having greater importance for increasing their PR because they help a lot in increasing links popularity to other websites and in return it will bring in much needed traffic to your