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: