Question mark
Use no spaces before a question mark and one space after. If a direct question is preceded by an introductory phrase or clause, the first word of the question may be capitalized. It doesn’t have to be, but this adds a formal feel to the sentence. A question mark should be placed inside quotation marks or parentheses only when the quoted or parenthetical matter is a question.

Usage
1. Direct questions

Example: Did he leave?

2. Questions embedded within a sentence

Example: How soon will he arrive? she wondered.

2A. but is not used in an indirect question

Example: She wondered how soon he would arrive.

3. A series of questions within the same sentence

Example: How is your sleep affected by stress? drinking caffeine? drinking alcohol?

4. Can be used to turn a declarative statement into a question

Example 1: You don’t mind if I borrow your red sweater?
Example 2: You’re not excited?

5. Rhetorical questions: the question mark is optional

Example 1: What difference does it make. (Rhetorical and pessimistic)
Example 2: What difference does it make! (Rhetorical and possibly argumentative)
Example 3: What difference does it make? (More interrogative than rhetorical)

6. If a command is phrased, for politeness, as a question but is still essentially a command, no question mark is used

Example: Will you please put your dirty dishes in the sink. (As spoken by a parent to their child)

6A. But if it’s really a question, then use a question mark.

Example:Will you please put your dirty dishes in the sink? (When spoken as an earnest question)

7. A question mark can be used to create a feeling of stream of consciousness (stylistic usage)

Example: Was your trip everything you hoped? Did you meet any interesting people? learn something new? see anything you’ve never seen before?