In formal settings, you must follow the rules governing the case of pronouns.
If your sentence calls for the subjective case, you must use I, you, he, she, it, we, you, they (see the subjective-case columns in the two tables above).
If your sentence calls for the objective case, you must use me, you, him, her, it, us, you, them (see the objective-case columns in the two tables above).
The trick, then, in speech and in writing, is to recognize instantly the grammatical function of the noun being replaced by the pronoun and then to plug in the correct pronoun without batting an eye.
Here are four pitfalls to watch for:
Pronoun Following the Verb To Be
1. A noun following the verb to be (or other linking verb) is a subject complement or predicate noun, which requires the subjective case of a pronoun taking the place of the noun:
Wrong: Knock, knock. Who’s there? It is me.
Right: Knock, knock. Who’s there? It is I.
Wrong: Who do you think did it? It could have been her.
Right: Who do you think did it? It could have been she.
Now that’s the way you ought to write. But when you’re having a cold one with friends at your favorite watering hole, you won’t impress Bubba the Bartender very much by saying:
It was I who ordered the Perrier with lime.
You’ll go much further in life, at least at Bubba’s, by violating the rule of pronoun case and saying:
It was me who ordered the Corona.
For advancement up the social ladder at Bubba’s, I’d suggest changing your drinking fare along with your pronouns. You may keep the lime.
Click page 2 below.