Look for sites in your niche, be very specific, and add something to the conversation if you're commenting. Don't do it for the backliink, there is so much more benefit from developing a relationship with the blog owner and developing your own private network with multiple people/sites.
You have to find your self. you should search on Google by your business term & also mention high page rank word. so you will get lots of data . refine them and use them
I think rather than picking the obvious blogs pick a few with low traffic then between you you can both boost your ranking