0 used with a more important verb in questions and negative statements -- Hilfsverb in Fragen und bei Verneinung
1 used with a more important verb for emphasis -- Hilfsverb zur Betonung
2 used to avoid repeating a verb which comes immediately before -- statt Wiederholung des Verbs
3 used to make question tags -- zur Formulierung von question tags
She lives in New York, doesn’t she?
4 used with a more important verb after seldom, rarely and little -- bei Inversion