Ask them If it's haunted or has been.... Hahaha my dad said if you ask they have to tell... Sorry that's the first thing that came to my mind. But maybe stuff like how old is it? Is the neighborhood safe? How's the pluming? Just general stuff about what kinda condition it's in your anything you'd like to know about it?
Has a home inspection been done? Ask if there are any known problems with the home, and how much it costs to repair these things. Ask for information about the neighborhood.
Always ask how old the roof is... if it's a really old house, ask about the electrical wiring.
i always thought they talk you into buying it so i felt they don't say the truth.