什么 [shénme] what qué
怎么 [zěnme] how cómo
怎么样 [zěnmeyàng] how about it qué tal
谁 [shéi] who quién
哪儿 [nǎr] where dónde
哪里 [nǎlǐ] where dónde
哪(一)个 [nǎ (yí) ge] which cuál
为什么 [wèishénme] why por qué
什么时候 [shénme shíhou] when cuándo
谁在唱歌？ (Shéi zài chànggē?) - Who is singing?
你想吃什么？ (Nǐ xiǎng chī shénme?) - What do you want to eat?
他什么时候来？ (Tā shénme shíhòu lái?) - When will he come?
你去哪里？ (Nǐ qù nǎlǐ?) - Where are you going?
为什么今天不上班？ (Wèishénme jīntiān bù shàngbān?) - Why aren't you going to work today?
这个问题怎么解决？ (Zhège wèntí zěnme jiějué?) - How to solve this problem?
General Questions (一般疑问句)
These questions ask for confirmation and usually have a "yes" or "no" answer. They often end with words like "吗 (ma)", "呢 (ne)", or "吧 (ba)".
你吃饭了吗？ (Nǐ chīfàn le ma?) - Did you eat?
今天天气很好，是吗？ (Jīntiān tiānqì hěn hǎo, shì ma?) - The weather is good today, isn't it?
他们在学习呢？ (Tāmen zài xuéxí ne?) - They are studying, right?