We could cover correct comma usage for days. I'll spare you a lengthy post, or multiple posts, and just cover some of the more common instances.
The Oxford Comma, a.k.a. the serial comma
If you choose to use this, we do here at Midwest Meetings, that means you separate the elements in a series with a comma. "I like playing piano, reading, and listening to music." If you choose to not use the Oxford comma, you would write: "I like playing piano, reading and listening to music."
There are all kinds of arguments about why you should, or shouldn't, use the Oxford comma. In your own writing, it's a personal choice. If you're writing for your company, refer to the company's style guide.
Separating Independent Clauses
Use a comma to separate independent clauses (sentences that can stand on their own). These clauses are joined by "and," "but," "for," "or," "nor," "so," or "yet." For example, this is correct: "My friend is very smart, and I've learned a lot from her."
Separating an Introductory Word or Phrase
Introductory words or phrases are often added at the beginning of a sentence. These require a subsequent comma. For example, "Last summer, I went on an amazing vacation." Or, "However, this year I can't afford a trip." You may also see "after," "although," "when," and "while."
Simple, but often overlooked. Any form of direct address is always followed by a comma. "John, please bring me a glass of water." "Happy Birthday, Sarah." And, of course, the life-saving reference in the image above: "Let's eat, Grandpa!" We certainly don't want anyone eating their Grandpa!
As I mentioned, there are a number of other topics covering comma usage. If you have a question on something I haven't covered here, please let me know! Either comment below or send me an email!