The topic of commas came up today. And it brought to mind a trend I see often regarding lists, as well as other common mistakes I see with comma usage. Commas fill up the biggest chunk of my Gregg Reference Manual. I’m not going to go through it in its entirety, but I will mention a few items. A comma isn’t necessary with every ‘and’ used in a sentence. I notice a lot of people omit the final comma before ‘and’ or ‘or’ in a list. That’s okay. Just remember to be consistent throughout your work.
For example:
- I went to the park, played on the big toy and went home. RIGHT
- I went to the park, played on the big toy, and went home. RIGHT * My preference
- I like pepperoni, sausage and meatballs on my pizza. RIGHT
- I like pepperoni, sausage, and meatballs on my pizza. RIGHT * My preference
All the above are grammatically correct. Personally, I prefer the comma before the ‘and.’ It offers more clarity. I’ve read that in journals, they omit the serial comma to save space. However, if the sentence leads to ambiguity, definitely include the comma.
For example:
- I often write about Jack, a friend and a businessman.
Is Jack a friend and a businessman? Or did I write about three different subjects?
A comma before a conjunction (and, or, but) is grammatically correct if there are two independent clauses. Like the serial comma, some choose to omit the comma. Not my preference, but to each their own.
For example:
- I went to the park, and Jim followed. RIGHT *My preference
- I went to the park and Jim followed. RIGHT
- I had pizza, and I had hot wings. RIGHT *My preference
- I had pizza and I had hot wings. RIGHT
Each of the above examples have two subjects and two verbs. A comma is not needed if there are two subjects and one verb or one subject and two verbs. AND should NOT be used. 
For example:
- Jim and I went to the park. RIGHT
- Jim, and I went to the park. WRONG
- I ate pizza and hot wings. RIGHT
- I ate pizza, and hot wings. WRONG
Just quick grammar tips.
