Figuring out the threading - English or (less common) Italian or (way less common) French is independent of figuring out the taper standard. Two ways of figuring out the latter. One is by brand (Campy, Stronglight are ISO, nearly everything else is JIS), the other is to fit a crank over the taper and see if it goes on too far (in the case of JIS crank on ISO taper) or not far enough (in the case of ISO crank on JIS taper).
Why do you ask? If you gave more info with your question, we could answer it better.