Is it boy's or is it boys'?

On my Be Romantic blog I am currently going over some of the basic elements in editing. My latest post concerns the proper usage of nouns and pronouns. One of my personal biggest problems is remembering how to punctuate possessive nouns correctly. For example: Is it boy's? Or is it boys'? Actually it can be both, depending on what you mean. The first (boy's) is singular possessive. The second (boys') is plural possessive.

The following is some other basic information on using Nouns and Pronouns: (English teachers, please be patient with me. I may have missed some other important things to remember.)

Usage of Nouns
• They can refer to a person, place, or thing.
• As the subject: The doorman greeted everyone.
• As a direct object: She sold her house.
• As an indirect object of a verb: Sam gave the cat a ball of string.
• As an object of a preposition: He called for directions over the phone.
• As an adverb: School starts today.
• As an adjective: The red car left the parking lot.

Possessive Nouns
• Singular Possessive: Add ‘s (boy—boy’s)
• Plural Possessive, plural noun that ends in s or es: Add an apostrophe to the end of the word (candles—candles’ OR ships—ships’)
• Plural Possessive, for plural nouns any other way: Add ‘s to the end of the word (children—children’s OR women—women’s)
• Individual Ownership: To show individual ownership, make both nouns in the sentence possessive. (Tom’s and Greg’s cars were stolen.)
• Joint Ownership: To show joint ownership, make only the final noun possessive. (Tom and Greg’s car was stolen.)

Pronouns
• Pronouns replace one or more nouns or a group of words in a sentence. They can be used to refer to a person, place, or thing.
• First Person Singular: I, my, mine, me, myself
• First Person Plural: we, our, ours, us, ourselves
• Second Person Singular: you, your, yours, you, yourself
• Second Person Plural: you, your, yours, you, yourselves
• Third Person Singular: he, she, it, his, her, hers, its, him, himself, herself, itself
• Third Person Plural: they, their, theirs, them, themselves

Capitalization of Proper Nouns and Adjectives
• Personal names: Thomas Edison
• Personal titles used as part of a person’s name: Dr. Sarah Stone, Greg Elderly, Ph.D., Pop John Paul II, Queen Elizabeth
• Business firm: Best Buy
• Business products: Kleenex, Pepsi
• Institutions: Hutchinson Omnisphere, Kansas State University
• Government bodies and agencies: Internal Revenue Service, United States Post Office
• Public organizations: Chamber of Commerce, Girl Scouts
• Private organizations: Midwest Authors Guild
• Family relationships when the word is substituted for a proper noun or used with the person’s name: I told Mother that my sister would be late. OR Grandma Ivy loves children. OR We went to stay with Aunt Lizzie and Uncle Otto.
• Nationalities and races: Australian, Chinese, Black (racial group)
• Languages: English, Korean
• Religious names and denominations: Christianity, Islam, Methodism
• Names of deities and revered persons: the Almighty, Allah, Child of God, Holy Ghost, the Word
• Names of sacred works: the Bible, the Koran, Genesis, the Beatitudes
• Religious holidays: Christmas, Easter, High Mass, Lent
• Historic events, special events, and holidays: Battle of Midway, Columbus Day, Han Dynasty, Hundred Year War, Midwest Book Fair, World War II
• Historical monuments, places, and buildings: Arlington National Cemetery, the Latin Quarter, Times Square, Washington Monument
• Geographic names and regions: Capitalize all geographic names and regions of a country, continent, or hemisphere. California, Niles Township, Western Hemisphere, Baja Peninsula, Strait of Magellan, Myrtle Beach, Lake Tahoe, the Andes, Aswan Dam, Red Wood Forest
• Geological terms: Capitalize the names of eras, periods, epochs, and episodes. Ice Age, Lower Jurassic period, Paleozoic era, Pliocene epoch
• Titles of Publications: Capitalize the first word and all other words except articles and prepositions under five letters in the titles of books, chapters, magazines, articles, newspapers, musical compositions, and other publications. Swan Lake (opera), The Tale of Two Cities (book), “The Midwest’s Blue-collar Blues” (article), “Essentials of Punctuation” (chapter), Kansas City Star (newspaper)