How to tell if you need that comma

One of my biggest pet peeves lately is the incorrect use of commas. And today, when I saw a terrible comma splice in an article written by the Associated Press on its website, I felt compelled to share my knowledge.

I don't profess to know every grammar rule in the English language, and of course, I do make mistakes in my writing from time to time.

But, I do know how to determine if you need a comma in your sentences. The AP sentence written incorrectly is here:

"Security Minister Pompeyo Bonilla pledged to impose order in the violence-plagued province, and dispatched a contingent of police and soldiers to the area."

In my basic reporting class at UF, Professor Mike Foley (my favorite) gave us a really quick & easy way to determine if a sentence needed a comma.

If the two phrases in your sentence can each be written as its own sentence (each phrase has a noun and a verb), then you need a comma. If not, the comma is not necessary. For example:

Mike and I went to the store and bought a gallon of milk. 
No commas required because "bought a gallon of milk" cannot stand alone as its own sentence.

Mike and I went to the store, and then Mike went home.
This sentence requires a comma, because both phrases could stand alone as independent sentences: (Mike and I went to the store. Then Mike went home.)

Next time you start to put a comma before the "and," apply this little test to avoid irritating me with your comma splices. Oh, and also to appear intelligent.