So what exactly am I talking about? You know, when you are emailing your friends and you want to say
Come to the movies tonight. Jordan, Harper and I are going.Which is somehow different from
Darcy has invited Jordan, Harper and me to the movies.But why should it be different? Well, because I is a subject pronoun and me is an object pronoun. Their purpose in the sentence decides which one you should use. This roughly translates to mean that after verbs and prepositions use me; before verbs use I.
So, looking at our examples
Come to the movies tonight. Jordan, Harper and I are going.In this example, the names are all listed before the verb ('are') so we use I.
Darcy has invited Jordan, Harper and me to the movies.The list of names is after the verb ('invited') so we use me.
And what was that surefire tip of Grandad's? The one that meant that you didn't have to know what a verb or a preposition was?
Take out the other names in the sentence and see if it still works.
Come to the movies tonight. I am going.
Darcy has invited me to the movies.It works!