1. Use commas to separate independent clauses when they are joined by any of these seven coordinating conjunctions: and, but, for, or, nor, so, yet.
2. Use commas after introductory a) clauses, b) phrases, or c) words that come before the main clause.
3. Use a pair of commas in the middle of a sentence to set off clauses, phrases, and words that are not essential to the meaning of the sentence. Use one comma before to indicate the beginning of the pause and one at the end to indicate the end of the pause.
4. Do not use commas to set off essential elements of the sentence, such as clauses beginning with that (relative clauses). That clauses after nouns are always essential. That clauses following a verb expressing mental action are always essential.
5. Use commas to separate three or more words, phrases, or clauses written in a series.
6. Use commas to separate two or more coordinate adjectives that describe the same noun. Be sure never to add an extra comma between the final adjective and the noun itself or to use commas with non-coordinate adjectives.
This is an additional source with detailed explanations and two practice quizzes
Use of colons
Colons follow independent clauses (clauses that could stand alone as sentences) and can be used to present an explanation, draw attention to something, or join ideas together.
Common uses of colons
To announce, introduce, or direct attention to a list, a noun or noun phrase, a quotation, or an example/explanation. You can use a colon to draw attention to many things in your writing.
- Lists/series example: We covered many of the fundamentals in our writing class: grammar, punctuation, style, and voice.
- Noun/noun phrase example: My roommate gave me the things I needed most: companionship and quiet.
- Quotation example: Shakespeare said it best: “To thine own self be true.”
- Example/explanation example: Many graduate students discover that there is a dark side to academia: late nights, high stress, and a crippling addiction to caffeinated beverages.
Use of dashes
Prepositional phrases modify nouns and verbs while indicating various relationships between subjects and verbs. They are used to color and inform sentences in powerful ways.
Parts of a Prepositional Phrase
In simplest terms, prepositional phrases consist of a preposition and an object of a preposition. Prepositions are indeclinable words that introduce the object of a prepositional phrase. Indeclinable words are words that have only one possible form. For example, below is a preposition, but belows or belowing are not possible forms of below.
The noun phrase or pronoun that follows the preposition is called the subject of the preposition. For example, behind the couch is a prepositional phrase where behind is the preposition and the noun phrase the couch acts as the subject of the preposition. Sometimes adjectives are used to further modify the subject of the preposition, as inbehind the big old smelly green couch.