Question marks behave in a similar manner to full stops in that they define the end of a sentence. The difference is that they are only used if the sentence is a question. As with a full stop, when used at the end of a sentence, it is followed by a capital letter.
When part of direct speech, the question mark goes inside the inverted commas, which will be looked at in another section.
'Do you want to come to the cinema?'
'No thank you.'
There are some cases that behave in a different manner, and need to be looked at here.
If the question is an indirect question, it needs a full stop instead of a question mark,
Direct question: 'Are you going out?'
Indirect question: I wonder if she's going out.
In other similar situations, a direct question needs a question mark, but an indirect question needs a full stop.