Use question marks for questions:
Will my mother ever change?
Put the question mark at the end of the question, not necessarily at the end of the sentence:
Will my mother ever change? I ask myself.
Do not use question marks for statements of doubt:
I wonder if my mother will ever change.
Do not use a question mark for a sentence that has the form of a question but is actually a polite request or is otherwise not intended to elicit an answer: