In the social space, there's power in being reactionary.
Comments are catalysts. They can boost a blog post up through Google search rankings. They make a status update more visible on Facebook. They often tell a more entertaining story than the news articles above them.
And if you are trying to build a meaningful presence online, you need to give comments if you want to get them. What types of comments should you be making?
Insightful ones. Seems like a no-brainer, but...well, just take a look at what some people put out there. Your comments should read like you cared enough to digest the content and then form independent thoughts around it.
Comments that move the conversation forward. If your viewpoint is unique and assertively — but respectfully — worded, it should inspire others to read and react.
Comments that ask for more information. It's OK to ask for clarifications or pose questions in comments. Doing so invites the author of the accompanying article to jump in.
Comments that answer questions. Likewise, when someone poses a question, giving a thoughtful answer can help you establish authority on the topic being discussed.
In the end, commenting is about thoughtful participation in an online experience. If you participate regularly in this manner, then chances are that you will inspire others to do the same for the content you create.
What else in your mind constitutes a good comment?