Not sure exactly what you mean.Do you mean where to place the question mark? (at the end) or do you mean question word DO (at the beginning) DO you live in China? What DO you like to eat?

You mean a do question? Do you like apples? Do you want to go to the movies? Do you dance salsa?

You use it in ALL questions in PRESENT tense with active and stative verbs (not with auxiliary like to be, or modals can, could, may..) When do you come back? Why do you need that? What do they study? Where do we live? What do I have to do? Who do you work for? with to be you dont need DO only change the word order. He is ready. Is he ready? (no DO)