Capitalization helps lend importance to certain words used in writing. It also improves the clarity of writing. For instance, capitalization helps the pronoun "I" stand out. Correct capitalization will improve the professionalism of your writing and will soon become second nature.
1: Capitalize the first word of a sentence
After any piece of ending punctuation, the next word should be capitalized. Ending punctuation includes full stops (.), exclamation marks (!) and question marks (?).
2: Capitalize proper nouns
Proper nouns are nouns which refer to a specific thing. Examples include people's names, place names and brand names. This capitalisation rule applies to the points of the compass: they are capitalized when they refer to a specific location, e.g. South Australia. It also applies to organizational names such as bureau or department. These are capitalized when they refer to a specific organisation and this usually is introduced in the specific work you are writing, e.g. if you refer to "the Department of Education and Training", you would capitalise "Department".
3: Capitalize first word of a direct quote
A direct quote is what you find between quotation marks. Example: She said, "This is not acceptable."
4: Capitalize the pronoun "I"
Wherever it is used in a sentence, this first person pronoun must always be capital.
5: Capitalize position titles when they come before a person's name
For instance, you would capitalize "chairperson" when writing "Chairperson Jones". When used in place of the name, the title is not capitalized except in the case of nouns designating a family member such as Uncle, Mum and Dad. Contrast "I love my mum." and "I love Mum."
6: In correspondence, capitalize all words in a salutation and the first word of a closing
For instance, a salutation will say "Dear Sir/Madam" and the closing should be "Yours sincerely".
7: Capitalize titles
Titles of books, movies, poems and so forth capitalize all important words, verbs and nouns as well as the first word. Generally, articles are not capitalized and prepositions and other words of less than three letters are left in lowercase. For example, "The Lion, the Witch and the Wardrobe".
Often article titles are an exception to this and only the first word is capitalized. For instance, this article would be titled "When to capitalize words" not "When to Capitalize Words".
8: Capitalize after a colon only when it introduces two or more sentences
Lists and single sentences following a colon are not capitalized. For example, in the excerpt "I've written about my topics for Helium: writing, movies, food and more." the word "writing" is not capitalized.
9: Capitalize names of days and months
Unlike Spanish, English capitalizes the names of days and months: Tuesday, January, etc.
10: Capitalize titles and positions when used as terms of direct address
For instance, "What's wrong with me, Doctor?" and "How are you today, Miss?"