Actually all words can use in both writing and speaking.
Just maybe some of them will be used more often in writing or in speaking, so the difference appears.
But don't need to worry about this, and you may need to talk to people more often so that you will know how to speak it in a natural manner.
Such as "怎樣“ and "如何" , we use ”怎樣“ more often but ”如何“ is right, too.
今天天氣怎樣?= 今天天氣如何?
Hope this helps. Nice day! =))