Grammar Tips. Comma 18.

Use a comma before a coordinating conjunction that joins two independent clauses.

Independent clauses are those that can stand alone as complete sentences. The most common coordinating conjunctions are: "and," "but," "or," "so," "for," and "nor." These conjunctions are used to connect words, phrases, or clauses that have equal importance in a sentence. They help to join ideas together and show the relationship between different parts of a sentence. 

INCORRECT: Do you want to continue with the Q&A or do you want to move to the lecture?

CORRECT: Do you want to continue with the Q&A, or do you want to move to the lecture?

CORRECT: She purchased the car, but she did not accept the extended warranty.

CORRECT: Team A put the plan together, and team B implemented it.

INCORRECT: I lost my job so I can’t pay my bills.

CORRECT: I lost my job, so I can’t pay my bills.