Do I use the comm, here, no, not there, here,?

I've always enjoyed commas. They look great and it feels like you can use them anywhere. Unfortunately, I have never quite fully understood exactly how to use it. I have always just stuck them in where I would rather be safe than sorry. I liked this quote about commas from Purdue University Online Writing Lab.
"The comma is a valuable, useful punctuation device because it separates the structural elements of sentences into manageable segments. The rules provided here are those found in traditional handbooks; however, in certain rhetorical contexts and for specific purposes, these rules may be broken."
I think that's a great explanation on how to use commas on a basic level.
http://owl.english.purdue.edu/handouts/grammar/g_comma.html