The colon (:)
The colon is almost always used after a complete sentence. It is used to indicate that what follows is an explanation of what precedes.
These are the things we need to buy: four chairs, one table, two fans and a mixer grinder.
The problem is this: which came first, the hen or the egg.
The conclusion we have arrived at is: if we want peace we must be prepared for war.

The colon can be used to introduce a quotation.

Shakespeare said: “Neither a borrower nor a lender be.”
Francis Bacon said: “Knowledge is power.”

The Interrogative mark (?)

The interrogative mark is used after a direct question:
Where are you going?
What is your name?
Who are you?

Note that we do not put the question mark after an indirect question.
He asked me what my name was.
He asked whether I had seen him before.
She wondered why I was not listening to her.

The interrogative marks are also not used after a polite request.
Would you mind moving a bit.
Would you mind passing the salt.

The Exclamation Mark (!)

The explanation mark is used after phrases and sentences expressing sudden emotion or wish. Avoid the frequent use of exclamation mark.
What a terrible storm!
What a beautiful flower!
Sometimes an exclamation mark is used after a short and peremptory order:
Get out! I don’t want to see you anymore.
Shut up! I don’t want to hear a word.

Inverted Commas

In direct speech, inverted commas or quotation marks are used to enclose the actual words of a speaker.
He said, “I don’t want to live anymore.”
She said, “I don’t know what I am going to do.”
Pope says: “The proper study of mankind is man.”