Final answer:
Proper use of commas is facilitated by understanding when to use them, such as after introductory elements, between items in a series, and before coordinating conjunctions in compound sentences, but not to separate essential information.
Step-by-step explanation:
When it comes to inserting commas correctly, understanding the rules is key. Reviewing the example sentences you provided, here are the corrected versions with commas in their proper places:
- I finally found my keys, and I got to work just in time.
- Mrs. Contreras threw out her old coffee table and cleaned the carpet.
- Taking the elevator to the roof, we hoped we could see the skyline and the bay.
- Though Susan wasn't feeling well, she went to the store anyway and bought ice cream, pizza, and candy.
- I let my neighbor borrow my phone because she said hers was tapped by the police.
It's important to know not to place commas around essential information, which is necessary for understanding the sentence, as opposed to nonessential information, which can be set off by commas without altering the meaning of the sentence. Also, the serial (Oxford or Harvard) comma is used for clarity in a series, and a comma should be used after an introductory element or dependent clause when it precedes an independent clause.