Some of you may remember memorizing the cases of pronouns in your grammar classes. Boring. And confusing. And for most of us, something we only need to think about when we're dealing with compounds.
But even then, we don't have to worry about cases.
There's a quick editing trick that will help you figure out which pronoun form to use in a compound. Let's say you're editing this sentence,
When she and Carrie danced on the table in the bar, everyone watched.
Should it be she and Carrie or her and Carrie? Start by isolating the relevant part of the sentence. The relevant phrase is:
she and Carrie danced
The compound is what causes the confusion. If you split the compound into two pieces, you get,
That's correct. We wouldn't say her danced.
This also works with other kinds of compounds, not just subjects. So if you had something like,
I wanted to go to the moon with Neil and he.
You could split the compound object of the preposition,
and you can see the error. Should be with Neil and him.
Nominative case? Objective case? Who cares? Just break them apart, and the form of the pronoun should be obvious.