I was always taught that one of the primary uses of a comma is
for when you're divvying up unnecessary parts of sentences (I'll
just go ahead and assume that was right). So, when I'm
constructing sentences I will read the sentence without the
sections that have been sectioned off by commas and, if it makes
sense, I will proceed on to the next sentence. One thing I have
noticed, though, (particularly with the word "but") is that
people tend to construct certain sentences like this: "I'm not
particularly one for this type of music, but I love this song."
Now, in this case, the first part of the sentence is the
unnecessary part. So, without the first part, it would read:
"But I love this song." This obvious makes no sense, as it is
out of context and was not a reply to anything. Were it me, I
would have constructed it like this: "I'm not particularly one
for this type of music but, I love this song." This way, without
the first part it would read "I love this song." which,
obviously, makes more sense. So, which