We have so many participants in our class, it was hard to choose which blogs to click on! I found a couple of fellow librarians and read and commented on their blogs. I also found some fun videos people had posted in Thing 10. I generally clicked on the blogs based on their titles. I guess that teaches me that I should name my blog something that is relevant to its content so interested readers can find it. Several blogs I clicked on didn't have any or many posts, so I tried again...and again.
As the how-to-make-good-comments articles mentioned, don't comment unless you have something new/interesting/relevant to say. I often feel like my comments are just in the category of "good job," so I don't want to comment. I'm more of a reader than a commenter by personality.
It was nice to receive a comment from someone who isn't the instructor, although your comments are well-received too! It makes one feel validated.
If I had students blog online, I would want other students in the class to comment. If there are a large number of students, perhaps each can randomly be assigned to follow a certain group of blogs to guarantee that everyone is being read and commented upon. I would also make sure to give feedback to their blogs.