They are placed forward, but not necessarily in the beginning if the subject is included. Here's some questions in the most proper word order. 1. (그는) 왜 안 올까? = Why isn't he coming? 2. (너는) 어떻게 그걸 알았어? = How did you know that? 3. (너는) 어디(에) 사니? = Where do you live? 4. (나는) 언제 떠날까? = When shall I leave? As you can see see the subject comes in the beginning before the question word. But since Korean sentences commonly omits the subject when the context provides it, you'll often see the question word in the beginning (In the above examples, only #1 might need the subject included). In addition, Korean is more flexible with word order, so even when the subject is mentioned, you may change the order for different emphasis or nuance. #1 and #2 below sound fine with slightly different nuance. #3 and #4 are very colloquial. 1. 왜 그는 안 올까? 2. 어떻게 네가 그걸 알았어? 3. 어디 사니, 넌? 4. 언제 난 떠날까?

I'm only a learner, so i may be wrong. My understanding is that 'where' and 'why' generally go at the front of the sentence: 어디에 있어요? - where is it? 왜 이래는 거야? - Why are you (doing) this? But i have heard that, if you want to emphasis something you can move the question words around, but i'm not entirely sure about that. I just put the questions at the front. I hope this helps.