A question mark may or may not be appropriate in a phrase depending on the context. Question marks should not be used after inquiries disguised as requests. "Would you mind closing the door as you leave?" (In writing, similar requests should be phrased more succinctly: "Please close the door on your way out.") Question marks are often used in formal writing to express doubt or uncertainty.
Generally speaking, if what you're asking is something that can be answered with a simple "yes" or "no," it's better style not to use a question mark at all. It's assumed that the answer is going to be either yes or no, so there's no need to clutter the text with question marks every time someone might want to say something that could be interpreted as a question.
However, sometimes you may need to ask several questions of a single person, for example when taking an application interview or doing research. In these cases, it is acceptable to use a question mark to make sure that each question is heard clearly and documented accurately.
For example, you may want to ask several questions about a particular event in order to obtain sufficient information to write a accurate report. The question mark would look like this: "Do you remember where you were standing when you saw John walk into the room? I'd like to know how long he was inside the room before you heard him scream."
Please check again... No. This is a request, nearly a demand, not a question. But then, most of the examples here are. A frequent hedging method is to enclose the request in a question-like form of words. When writing something like, 'Could you kindly open the window, Jill?' I wouldn't use a question mark. I would instead write, 'Could you please open the window?' Here's an example from the web: "A request for information may be made in several ways, for example by email, letter or through the Internet."
In general, if you want someone to do something and don't want them to do it, use a question mark; if you want them to do something but don't mind if they don't, use "could"; if you want them to try their best to do something and don't mind if they can't, use "will".
'Could you pass me the salt, dear? Could you bring me some water, please?
Question marks are used in both official and informal writing, as well as for asking direct and indirect inquiries. They are one of the few punctuation marks that simply signify one thing. There is no need for other punctuation to indicate meaning within the quotation.
Question marks are used in quotations because they can be combined with other punctuation marks to provide more information about the source. For example, if I wanted to quote George Washington here, I could do so by adding an exclamation point and a quotation mark: "Exclamation points and quotation marks give context to your quote."
A question mark is also used at the beginning of a sentence when the speaker asks a general question without indicating any particular person or people. For example, if I asked you how old you were, I would use a question mark before age to indicate that age was a general term that could apply to many people.
Another common use for question marks is when giving instructions. If you want someone to repeat something, you can use a question mark and their name, like this: "Repeat what I said?" This tells them to repeat what you said earlier.
And finally, question marks are often used within quotations to indicate a word or phrase that was not understood.