Commas seem to be one of the greatest stressors for writers, including my clients. It makes sense–the comma is the most versatile punctuation mark and is used in so many different ways.
Adding to the confusion: there are instances where you–yes, you the author–get to decide whether or not to include a comma.
Here are a couple of times where you wield the power to bestow a comma (or not):
Comma before the terminal too (or though)
Sometimes writers end a sentence with too or though, thus making it the “terminal” (or ending) too. A comma can precede the terminal too, or not.
Correct: Joan Jett, I love rock ‘n’ roll, too.
Also Correct: Joan Jett, I love rock ‘n’ roll too.
Compound predicate comma
This has a lot of grammar jargon, so let me explain. The predicate is the part of the sentence that includes the verb and whatever follows it. In this instance, compound means more than one.
Here’s a sentence with a compound predicate:
I went to the concert and danced my booty off.
You do not have to separate compound predicates with a comma.
But you can as part of your writing style. Not every time, of course, but when you have a good reason to do so.
Maybe you’ve written a lengthy sentence, and you want to break it up a bit for the reader.
Another reason to use a compound predicate comma is to draw special attention to the second predicate.
Correct: Hoping to unleash my wild soul within, I went to the rock concert with a lively crowd and a favorite singer, but ended up sitting on my butt instead of rocking out.
Correct: Hoping to unleash my wild soul within, I went to the rock concert with a lively crowd and a favorite singer but ended up sitting on my butt instead of rocking out.