Since proper punctuation is an essential part of successful communication, remembering basic punctuation rules will make it easier for you to write clearly and effectively.
When punctuation is parallel it means that interrupting a main clause with a dash or a comma requires using the same punctuation at the beginning and end of the clause.
Incorrect: The teenagers, students from Mrs. Smith's art class—went on a field trip to the museum.
Correct: The teenagers, students from Mrs. Smith's art class, went on a field trip to the museum.
Correct: The teenagers—students from Mrs. Smith's art class—went on a field trip to the museum.
This rule also means that you should not use a semicolon to set off just one item in a list.
Incorrect: I have lived in Des Moines, Iowa, Seattle, Washington; and Boise, Idaho.
Correct: I have lived in Des Moines, Iowa; Seattle, Washington; and Boise, Idaho.
An emdash (the longest of the three dashes) can be used for many of the same purposes as a comma. A pair of emdashes can be used if the sentence already contains commas or to mark off information for emphasis; while a single emdash draws attention to a modifier or an extra piece of information.
Sarah hated walking to school—it was all uphill—but she had no choice, she had missed the bus again.
For his birthday, Mark received a sweater, a jacket, a savings bond—and a new bike!
Pizza, chocolate, and ice cream—these are my favorite foods.
If you have trouble deciding when to use a colon in your writing, it helps to ask yourself if a period or question mark would be appropriate in the same location. If the sentence is already complete, you may use a colon to add a list, elaboration, or restatement.
List: I have three brothers: David, Kent, and Jacob.
Elaboration: I have decided not to move to San Francisco: I have been offered a job in Milwaukee.
Restatement: Thinking back, Jenny wasn't sure who started yesterday's fight: She couldn't decide whether to blame herself or her best friend Annie.
In a compound sentence that has no coordinating conjunction, a semicolon joins related independent clauses that are of equal importance.
Sarah answered my question abruptly; she seemed preoccupied.
A semicolon can also be used before the conjunctive adverb used to join the two clauses in a compound sentence.
The restaurant was very crowded; however, the waitress took our order immediately.
Parentheses can be used to show elements in a sentence that are related, yet not necessary to understand the meaning of the sentence. Parentheses can be replaced by commas in most cases, although the use of parentheses tends to de-emphasize a piece of information.
My family visited several countries (Italy, France, and Spain) on our vacation last year.
If the information inside the parentheses forms a complete sentence within the larger sentence, no punctuation is necessary.
The snow (April saw it when she passed the window) completely covered the trees.
An apostrophe is used to indicate possession or ownership. An apostrophe and an -s should be added to singular possessive nouns, plural possessive nouns that do not end in -s, and singular possessive nouns that end in -s. Only an apostrophe should be used when showing possession or ownership for a plural possessive noun that ends in -s.
Singular possessive noun: Susan's book
Singular possessive noun ending in -s: Chris's car
Plural possessive nouns: the children's school
Plural possessive noun that ends in -s: my parents' house
An apostrophe can also be used to show that a letter has been omitted from a word to form a contraction. For example, "it's" is a contraction for it is. "Its" is a possessive pronoun.
If you are looking for more help with basic punctuation rules, check out the following online resources: