When to use a comma before "and":
* In a series of three or more items: "I went to the store for milk, eggs, and bread."
* When "and" joins two independent clauses: "The sun was setting, and the birds were singing."
When NOT to use a comma before "and":
* When "and" joins two words or phrases that are not independent clauses: "The red and blue car was parked outside."
* When "and" is used to show addition or continuation within a single clause: "The child was playing with his toys and laughing."
Example:
* Correct: "The dog barked, wagged its tail, and ran towards the door."
* Incorrect: "The dog barked, wagged its tail and ran towards the door."
Let me know if you have a specific sentence you'd like help with!