How would I say it?

      以前说英语时不知道该怎么说时,我总是会说:
I don’t know how to say it, 
      或者会说:
I don’t know how to express it,
      今天和Tim聊天,听到他说了句:
How would I say it.
      这句话很不错,赶紧记下了,呵呵。