When to capitalize:1. Capitalize any word that starts a new sentence.
2. Capitalize all proper nouns. This is a golden rule. If you do not know if you are using a proper noun, a dictionary will tell you. Proper nouns are words such as names, specific cities, specific states, specific countries, specific oceans, specific continents, specific mountain ranges, specific mountains, specific seas, specific monuments and specific wars or titles that are followed by a name. "The highest mountain in the United States is Mount McKinley."
3. Every word of a book, movie, song, painting, play or short story title other than an article (a, an, the) or a preposition (at, before, beside, between, down, during, except, for, from, in, into, near, of, over, on, onto, to, toward, under, with, without and any others that I have forgotten) should not be capitalized. There is an exception to the rule (of course). It is optional whether you capitalize any preposition of four letters or longer, though most people prefer not to capitalize any preposition.
4. Capitalize Mom, Mother, Ma, Dad, Father, Pa, Grandma, Grandpa, etc. if you are using the word as a name.
5. Capitalize parts of the country such as the Northeast, the South or the Southwest.
6. Capitalize monuments such as the White House.
7. Capitalize the first person pronoun, "I."
When NOT to capitalize:1. Do not capitalize a title unless a name follows the title. Even the president and the pope do not get special treatment. "During the Civil War, the president was President Lincoln."
2. Do not capitalize a relation unless the relation word is a name. "I called my mother, Mom."
3. Do not capitalize north, south, east or west if you are talking about a direction rather than a place. "In the Northeast, the ocean is east of the mountains."
4. Do not capitalize the words, "street" or "avenue" unless they are attached to a name. "The street that she lives on is Main Street."
5. Do not ever capitalize for emphasis or to give a word more power. A common noun is a common noun and common nouns are not capitalized.
6. Do not capitalize specific buildings unless they are monuments. "She lived in a white house on Salem Street that was about twenty miles north of the Empire State Building."
7. Do not capitalize the first word in a list that directly follows a colon.
8. Do not capitalize the first word in the second half of a split quotation unless it starts a new sentence or follows another capitalization rule (name or proper noun).
The most important rule to consider when you are deciding if you are writing a proper noun (capitalize) or a common noun (do not capitalize), is to consult a dictionary like "Webster's New Collegiate Dictionary." Yes, it does still exist. "Webster's Instant Word Guide," (little black book) is used to find correct spelling and often does not distinguish between common or proper nouns, so do not rely on it. If you are writing a query letter or if your writing will be judged, and you are unable to decide whether or not to capitalize, it would be better to rewrite the phrase or sentence in a way that eliminates the questionable capitalization.