1. Always start a sentence with a capital letter. You will need to capitalize the first letter of every sentence.
Here is an example of proper capitalization at the beginning of a sentence:
（1）She invited her friend over after school.
2. Use capital letters to start proper nouns and titles. What’s more, capital letters should also occur at the start of proper nouns and titles. Proper nouns are the names of specific people, places, and things. Titles are the names of works of art (books, movies, plays, etc.), institutions, geographical areas, and much more. Titles can also be honorifics (Her Majesty, Mr. President, etc.).
Titles and proper nouns consisting of more than one word should have every word capitalized, except for small words and articles like “the,” “an,” “and,” etc.
Here are a few examples of capital letters being used for proper nouns and titles:
（1）Genghis Khan quickly became the most powerful man in Asia, if not the world.
（2）In her opinion, Queen Roberta‘s favorite museum in the world is the Smithsonian, which she visited during her trip to Washington, D.C., last year.
3. Use capital letters for acronyms. An acronym is a word (or a “coined” word) formed from the first letter of every word in a long proper noun or title. Acronyms are frequently used to shorten long proper nouns.
Here is an example of acronyms made from capital letters:
（1）The CIA and the NSA are just two of the USA‘s many intelligence agencies.