Use the question mark:
1. At the end of all direct questions
- What is your name?
- Do you speak Italian?
- You're Spanish, aren't you?
2. At the end of all tag questions
- He should quit smoking, shouldn't he?
- He shouldn't have quit his diet, should he?
- They're not doing very well, are they?
- He finished on time, didn't he?
- She does a beautiful job, doesn't she?
- Harold may come along, mightn't he?
- There were too many people on the dock, weren't there? (Be careful of this last one; it's not "weren't they?")
For more information, please read "Question tags" section.
3. Do not use the question mark for reported questions
- He asked me what my name was.
- She asked if I was Spanish.
- Ask them where they are going.
General notes:
1. Don't forget to place a question mark at the end of long sentences that contain a question
- Isn't it true that global warming is responsible for more and more problems which are having a disastrous effect on the world's climate and leading to many millions of people in countries that can least afford it having to contend with more and more hardship?
2. Sometimes a question mark can be placed within a sentence
- There is cause for concern - isn't there? - that the current world economic balance is so fragile that it may lead to a global economic downturn.
3. When a question ends with an abbreviation, end the abbreviation with a period and then add the question mark.
- Didn't he use to live in Washington, D.C.?