For a general location:
* Где? (Gde?) - This is the most common and general way to ask "where?"
For a specific place:
* Куда? (Kuda?) - This is used to ask "where to?" or "to where?"
* Откуда? (Otkuda?) - This is used to ask "where from?" or "from where?"
Here are some examples:
* Где ты живешь? (Gde ty zhivёsh?) - Where do you live?
* Куда ты идёшь? (Kuda ty idёsh?) - Where are you going?
* Откуда ты приехал? (Otkuda ty priehal?) - Where did you come from?
It's important to choose the correct word based on the situation. If you're unsure, "Где?" is a safe bet.