Think of it this way, names of specific people, places and things are proper nouns. General or common nouns like school, province, country, mountain, and ocean, are not proper nouns and not capitalized. But specific names like Brown Elementary, British Columbia, Canada, Mount McKinley, and the Pacific Ocean, are proper nouns and must be capitalized. Even names of specific regions and specific buildings are capitalized such as the B.C. Interior, the Pacific Northwest, the Houses of Parliament.
There are many other instances where capital, or upper case, letters are required. There are so many in fact, you may have forgotten some. So I've listed 6 significant ones below:
- Words derived from common nouns are also capitalized. For example, Canadian comes from Canada, so it is capitalized
- The first word in quotations. For example, Shakespeare's famous words, 'To be or not to be'.
- A title for a person, if it is given with their name, or instead of their name, is always capitalized. For example, Prime Minister Trudeau. [But not, the prime minister of Canada is …]
- When you're writing a letter, the salutation and first word of a closing are capitalized. For example, you might right, Dear Mr. Smith … Sincerely, Janet
- Titles of books and movies, magazines, works of art etc. are capitalized. However, less significant words in names and titles are not capitalized. Prepositions like 'of', conjunctions like 'and', and articles like 'the' will not begin with upper case letters, as in for example, 'The Agony and the Ecstasy'.
- Letters in abbreviations and acronyms, or at least the first letters, are often capitalized. For example, B.C. for British Columbia, P.S. for post script, and Tbsp. for tablespoon. However, teaspoon is abbreviated as tsp. and road becomes Rd.
Upper case letters are very useful at indicating things like the beginning of sentences, and proper nouns. So it's important they are reserved for those special uses. Of course they can still be used to make titles and certain words stand out. But they mustn't be overused. Otherwise, the very useful jobs they perform will get lost in the clutter.