The question mark is used to ask a direct question, to indicate an editorial doubt, and to express surprise. Never double punctuate. Don’t use two question marks together or a question mark and an exclamation point.
Examples: When will Taylor’s car be ready?
The world population is estimated to be 7.029 billion? by the United States Census Bureau.
That is your answer?
A question mark is used within a sentence at the end of the direct question. If the question does not begin the sentence, it doesn’t need to start with a capital letter.
Example: The question, how long is this meeting going to last? was on everyone’s mind.
An indirect question never takes a question mark.
Example: He wondered if it was time to go home.
When a question within a sentence consists of a single word, such as who, when, how, or why, the question mark may be omitted, and the word is sometimes italicized.
Example: The question was no longer how but when.
A request disguised as a question does not require a question mark.
Example: Will the congregation please rise.