>I just finished a peer review on a classmate’s paper in Comp III and had this to say about the use of commas:

The one thing I would really pick out is your sentence structure. You are a great writer, but you need to stock up on commas and use them more generously. Heck, buy them in bulk. Whenever you proofread your own work, either say it out loud or try to hear it in your mind as it would be spoken. Whenever the voice pauses, not going immediately on to the next word but stopping just for a heartbeat, ask yourself: could I put a comma here? More often than not, the answer is yes. I like to think that the comma is how we encapsulate ideas for the reader on the phrase level; it gives their brain a half-second to process what they have just read. Without the comma, it requires more effort to understand what we are reading. They can even help us writers judge the best length for each sentence.

I’m going to save that bit for future peer reviews; personally, I think the comma is a commonly underused form of punctuation in personal writing.