For asking about a method or process:
* 怎么 (zěnme): This is the most common way to ask "how" in the sense of "how do you do something?"
* 如何 (rúhé): This is a more formal way of asking "how."
* 怎样 (zěn yàng): Similar to "zěnme," this is a colloquial way to ask "how."
For asking about a state or condition:
* 怎么样 (zěnme yàng): This is used to ask "how" in the sense of "how is something?" or "how are you?"
Examples:
* 你怎么做这个菜? (zěnme zuò zhè ge cài?) How do you make this dish?
* 如何提高我的中文水平? (rúhé tígāo wǒ de zhōngwén shuǐpíng?) How can I improve my Chinese skills?
* 你今天怎么样? (nǐ jīntiān zěnme yàng?) How are you today?
The specific phrase you use will depend on the context and the specific meaning you want to convey.