Capital Letters

Key Rule — When to Use Capital Letters

We use capital letters:

For the first word of a sentence.
For the personal pronoun I.
For proper nouns (names of people).
For days, months, and festivals: Thursday, April, New Year.
For nationalities, languages, and adjectives derived from countries: China, Chinese, Morocco, Moroccan.
For the names or abbreviations of organizations: United Nations, Educational, Scientific and Cultural Organization (UNESCO).
For the titles of films, books, and works of art: So Long Mr. Wrong, Rhapsody, Barefoot, She's the Man.
For the names of places (countries, cities, towns): Morocco, Singapore, Paris, London.

Punctuation

Key Rule — Full Stop

At the end of a statement or a sentence (information or instruction) and after a polite request:

My hearing is getting worse as I get older. Please forgive me.
In some abbreviations to show that some letters at the end of a word are missing: Pl. (plural), approx. (approximately), Fri. (Friday).
In modern British English, full stops are not usually added when the abbreviation contains the last letter of the full word: Mr (= Mister), Dr (= Doctor), Rd (= Road), Ave (= Avenue).
Full stops are not used after abbreviations of scientific units: cm, km, g, kg, sec, min.

Key Rule — Comma

To represent a brief pause in the middle of a long sentence: It's been hot every day so far, so we've spent most of the time on the beach along with everyone else.
In lists of adjectives that appear before a noun: a hot, sunny, long day. (Note: It is also correct to leave out commas in this case.)
In lists of two or more items: I bought some tomatoes, some mushrooms, and a pumpkin. (Note: The last comma before and can be left out.)
After linking words at the beginning of a sentence: First of all, let me introduce the plan.
Before and after linking words in the middle of a sentence: Chris, on the other hand, did not approve.
When we give additional information that can be left out: Ahmed, who is known for being lazy, woke up at 11:30.
Before question tags: You did your homework, didn't you?
To separate the speaker from the words spoken: Kelly said, "I'll be right back."
In large numbers to separate sets of digits: 2,300 – 18,700 – 450,060 – 5,000,000

Key Rule — Semicolon

To join two closely related sentences: We need better technology; better technology costs money.
To separate long items in a list: Students are asked not to leave bicycles by the entrance; not to eat chewing gum in the classroom; and not to be late for school.

Key Rule — Colon

To introduce an explanation of the previous part of the sentence: In the end, we had to stop: we were tired and it was very dark.
To introduce items in a list: We ask you to provide one of the following pieces of identification: a passport, a student card, or a driving licence.
To introduce examples in the middle of a sentence.

Key Rule — Quotation Marks

Around direct speech: "What time is it?" Susie asked.
Around words you want to emphasize or treat as special: What is "globalization"?

Key Rule — Question Mark

Key Rule — Exclamation Mark

To express strong emotions such as joy, anger, or surprise: You will not believe it! I got my driving licence!
With commands that should be obeyed: Stop laughing!
With short exclamations (interjections): Help! Ouch!

Key Rule — Apostrophe

With 's to show possession or connection: Chris is having dinner with Kelly's sister.
To show that letters are missing (contractions or short forms): I can't (cannot) believe you anymore; you're (you are) so exciting!

These explanations will definitely help you structure and build your writing in a clearer and more organized way.