I generally go with “A New Hope” or “Episode IV”, simply to make it avsolutely clear which one I’m talking about. To me just saying “Star Wars” makes things a bit confusing, what with that also being the name of the franchise and all.
Incidentally, from what I understand, in Norway the movie is still officially known as “Star Wars: Stjernekrigen”. The translated subtitle of “Et Nytt Håp” was only ever included on the 2004 DVD.