Nouns or pronouns can be governed by prepositions. These are called the objects of the prepositional phrase. Such nouns or pronouns are put in one of three cases:
A preposition may govern one or more cases.
The Nominative case never takes a preposition.
DETERMINING THE CASE:
In the examples below, prepositions expressing motion or rest are illustrated.
As a general rule, prepositions expressing motion to take the accusative
case, prepositions expressing motion from take the genitive case, and
prepositions expressing rest or lack of motion take the dative case.
With a little imagination, the illustrations can be made to work for other ideas of motion. Think of the left side of the illustration as the accusative side and the right side as the genitive side. Wherever the arrow ends indicates the case to be used. If there is no motion, then there will be an "X" within the circle, and in these instances, the dative case is used.