no change of vowel     singular (a) masculine (b) feminine (c) neutral   Nominative der Schuh die Frau das Kind   Genitive des Schuhes der Frau des Kindes   Dative dem Schuh der Frau dem Kind   Akkusativ den Schuh die Frau das Kind   plural     Nominative die Schuhe die Frauen die Kinder   Genitive der Schuhe der Frauen der Kinder   Dative den Schuhen den Frauen den Kindern   Akkusativ die Schuhe die Frauen die Kinder

There are two advices that the author would like to give:
a) As you can see there are only four cases of different endings: in Genitive for masculine and neutral form; and      in plural in Dative in masculine and neutral form.
b) If you keep in mind a) and the plural forms then the declension is just learning the definite (and later     indefinite) articles. And since the masculine and the neutral are the same in plural the number of articles is     quite limited.