- Find the conjugated verb, then its subject (who does the action?). The subject is in the Nominativ.
- Is there a preposition? It decides the case of the group that follows it (see the list below).
- If not, the verb decides. Most verbs take an object in the Akkusativ. A few common verbs take the Dativ (helfen, danken…).
- Two objects? With give, show, explain… the person is in the Dativ and the thing in the Akkusativ.
Der Lehrer erklärt dem Schüler die Regel.
Der Lehrer = subject (Nominativ) · dem Schüler = to whom? (Dativ) · die Regel = what? (Akkusativ)