Places Where Commas Don’t Belong.
Like knowing when to use commas, it’s also useful to understand where and why you shouldn’t indicate a pause. Below are five basic conventions. A more detailed understanding can be found in a library grammar book. But these pretty much cover the territory.
1. Do not separate a verb from its subject or object.
• Homes (subject) large enough to provide a bedroom for each resident became (verb) increasingly popular (no commas between resident and homes).
• Mother (subject) noticed that the children (object) were cranky after watching too much TV (no comma between mother and that).
2. Do not use commas in series if it makes no sense (remember the “and” test).
• It was a foolish, dangerous mission (no comma between dangerous and mission)
• The hospital was unsuitable for severely disturbed youth (no commas).
3. Do not use commas for mildly parenthetical expressions.
• She thought his work was essentially artistic (do not set off the expression essentially with commas).
• Her mother usually was awake by eight o'clock (do not set off usually with commas).
4. No comma between compound ideas connected with “and.”
• John did not realize his mistake was serious and that he would be getting in trouble with the law (no comma after serious).
• Mary and her sister Suzie went to a movie and then to Burger King for a snack (no comma after Mary or after movie).
5. Do not use a comma before a prepositional phrase.
• Kim fainted, her body slowly slipping under the table (no comma before under).
• Harry had to hurry and pick up his suit from the cleaners before they closed (no comma before from).
If you do need a comma for clarity, by all means, put it in.
• People who can, go door to door in case anyone needs help.
• My mother shops at Penney's, for she likes their service.