It is an important part of being a blogger to read and comment on other blogs. It helps you keep in touch with what other bloggers on your subject are up to, brings in new ideas and learnings, and helps you broaden your views and develop new perspectives about your own subject.
This is important because as we continue to write, we exhaust the things we originally wanted to say, and begin to get repetitive. Naturally, repetitive is boring. Also, unlike a book or a website, a blog is an evolving publication. Nothing here is frozen for all time, and it is a log of your own evolution as a person interested in the subject. Perhaps to be compared with a magazine with fresh issues each month to catch the readers interest.
Not evolving makes YOU boring. You don't want that.
Why comment? Remember the excitement you feel when someone comments on your blog? Well, other bloggers feel that too. Sharing the impact of the post on you is the easiest way to connect with an author. Connecting with other authors helps you build relationships in the online world, which mean a whole load of new things - links to your blog, references to you, blogging relationships, reputation, advertising income..... you get the people interested in you as a person, and you can get them to do a whole load of nice things for you.
Another way is of course to write about what they are up to on your blog. This needs some relevance to what you are up to. For example, we are now talking about blogging and commenting. Have you been to problogger.com? Darren Rose there has a fabulous way of writing about blogging in a way that leads to development of our skills and its really easy to read.
If you are interested in earning from your blog, look at John Chow's blog. Again, many useful tips and references that will help us.
So how do you go about reading and commenting on blogs? One way is to keep an eye out when you read something and look for opportunities to get in touch with the author. Now, inane comments are only going to irritate the author, but if you can share something others would want to know, people get interested in you quickly.
As an author for example, I enjoy knowing what my blog does to you. Do you feel happy, sad, irritated, inspired, challenged.....? When I go to other blogs, reading such comments give me an idea of the writer's relationships with the readers. Other comments I enjoy knowing is when you bring in a perspective that I hadn't thought of or add information that is not included in the original post.
Very often, and interesting comment makes me follow through to the commenter's link. I expect to find more of what I found interesting there. If nothing, I will follow links in comments on my own blog to see who is interacting with me. Never mind the search engines, even the kind of interest you can generate with this is quite high.
So if you want to do this actively, how do you go about doing it? What I usually do is I plan a post I would like to write, and search for blogs related with it as a part of the research. It gives me a good idea of the kind of approaches to the subject, as well as provides me the opportunity to interact with other writers on it. Then, I write my post and link to resources I found interesting and comment on the others sharing my experience of their posts and adding anything of value that occurs to me.
There are many ways of finding such blogs. Blog search engines, technorati, regular search engines are some. There are commenting softwares that make this much easier for you. They are able to search for blogs on a subject you specify that are open to comments. Comment Kahuna and Fast Blog Finder are two free examples. There are possibilities to look for page rank or no follow on links, etc, but their greatest strength is having a list of commentable blogs quickly lined up fo ryou.
While some bloggers frown on the use of such softwares, the real reason of the frowning is people leaving random comments on blogs that add no value and only spam links. If you are willing to read the posts and make an effort to comment in a way people would enjoy reading, the only difference the softwares bring in is that of removing places you can't comment on from your searches.
With judicious planning of the comments you make, it is possible to build links, relationships and a reputation in the online world.