Use commas when joining two independent clauses. Translation: Use a comma when slamming 2 sentences together.
Noun verb, and noun verb.
Noun verb, as noun verb.
Noun verb, for noun verb.
Noun verb, or noun verb.
Noun verb, while noun verb.
Noun verb, because noun verb.
Noun verb, but noun verb.
(Note on ‘but.’ The word ‘but’ is used to introduce an opposing statement to the first clause.) Example: He was handsome, but cruel. Positive, but negative. I wouldn’t mention it, but I have seen people write: She was sweet girl, but also nice. Can you believe it???? No, duh….
It is said that for every grammar rule there is an exception, and this is true in compound sentences. You many wish to write a compound sentence and you don’t want the reader to pause at the comma. You may want them to consume the entire idea in one breathless flash. Examples:
- The economy stagnates and prices rise.
- Valdez was a disaster but not as bad as the Gulf.
- People curse BP while driving in their cars. (Whahaha! Idiots.)
- Follow me or get lost.
My personal opinion: Do not over use this bit of trickery or your reader will feel like they’ve been in a marathon. Unless, of course, that’s the way you want them to feel. Maybe, your character is sliding down a canyon wall, drowning in a lake or rushing out the door for a hot date. Or, maybe, you just want to make a point.
Best advice: Read your stuff out loud. If you pause—however slight—then you probably need some punctuation.