Nominative case pronouns:
I
you
he, she, it
we
you
they
Objective case pronouns:
me
you
him, her
us
you
them
Look at:
Paul and *** I *** decided to go to the library to find a magazine.
"I" is a pronoun in the nominative case.
All pronouns in the other sentences, "him", "us", and "me" are objective case.