Backlinks Question

When I am doing blog commenting should I only be commenting on sites that have something to do with my niche or could I comment on high PR sites that dont have anything to do with my niche?

Focus on higher pr ranked sites and sites that pertain to your niche

well as my personal experiance says comment on high pr blog and you dont need to comment a very good critical analysis of a blog just say"hey you have sucha nice blog thabbks for sharig this info"and 90%of blog admin will not delete that comment so enjoy baclinks for high pr blogs