You don’t have to write a blog to take advantage of them. By leaving comments on blogs, you can establish yourself as an authority to that blog’s regular readers, who may find their way to your website.
If you want to drive traffic by leaving comments, make sure you create a profile, if possible, with your website address, so other readers will have an easy time finding you. Blogs without commenter profiles usually still let you include your website. Make sure you do.
Also, keep your identity consistent across the blogs on which you comment. I recommend using a variant of your real name (I am usually “samglover”) rather than a nom de plume. It will make you easier to find.
Finally, sign up for Twitter and let others know what you are reading and commenting on.
(photo: Wikimedia Commons)