Between you and I, being both a linguist and an editor sometimes leads to conflicting feelings — and, just between you and me, phrases such as "between you and I" can really get under my skin sometimes.
Did you wince when I started with "between you and I"? If you did, you'll really hate what happened to me a year or so ago. I was walking down the street and a young woman said to me, "Excuse me, can you take a picture of my friends and me?" And then she said, "Sorry for the grammar."
"Sorry for the grammar?" I asked.
"'My friends and me' should be 'my friends and I,'" she said.
"No, actually, in that instance, 'my friends and me' is correct," I said. Then I took the picture for her.
As I was walking away, she said to one of her friends, "Is that right?"
And he said, "No, it should be 'my friends and I.'"
Would you want to smite him? If you're a grammar stickler, you probably would. I wanted to. But I just kept walking.
But let's not get into why people — including me — get so upset about grammar. That's a whole other article. What I do want to do is address this "and me"/"and I" issue from two perspectives: the editor and the linguist.
Editor first. The rule for when to use which is actually very simple. Wherever you would say "me" you say "…and me"; wherever you would say "I" you say "…and I." So "I take a picture" and "My friends and I take a picture"; "Take a picture of me" and "Take a picture of my friends and me."
Of course, after "between" there's never just "me" or "I." So here's another simple rule: the only time you use the subject form — I, he, she, we, they — is when it's the actual grammatical subject of the verb: the "I" in "I take a picture," for instance. Anything that is the object (complement) of "between" or any other preposition is not the subject of a verb.
So "between you and me" is always correct and "between you and I" is never correct. Simple.
OK, time for the linguist to take over: If it's so simple, why do so many people have so much trouble getting it right? These same people would never say, "Take a picture of I" or "Give it to I." They have an automatic understanding of the rules of English subject and object forms… except in compound noun phrases.
This isn't evidence of the woeful state of English language education. People, often quite literate people, have been doing this for centuries. More than 400 years ago, Shakespeare had a character in The Merchant of Venice say, "All debts are cleared between you and I." His contemporary Ben Jonson wrote the line, "Musco has been with my cousin and I all this day" in Every Man in His Humour. Examples between then and now abound. The obvious fact is that the simple rule is not automatic, even if you grew up speaking English. It has to be learned, and not everyone learns it.
Here's what many linguists think is going on. A verb gives its subject what's called "nominative case" — it's as though it gives a suitcase containing an "I" suit to the "me," and the "me" puts it on and becomes "I." But when a pronoun is in a compound ("you and I"), it's as if the compound is a car holding the nouns and/or pronouns in it, and the case assigner doesn't reach inside, it just puts the case on the roof. You have to learn to give the case to the passengers before they drive on out of your mouth or it will fall off and stay behind. (If you want to read about this in much more technical depth, start with this article on Language Log.)
A result of this is that kids who would never say "Me am going to the store" will say "My friends and me are going to the store." They don't give the case to the nouns in the compound. But at a certain point they may get corrected often enough — "It's 'My friends and I'" — that they learn that "and I" is the correct form. Or they learn it from hearing adults say "between you and I" and "Take a picture of my friends and I."
What they should learn, according to the formal standard rules, is that it's "and I" only wherever it would be "I"… but many people instead just learn that "and I" is correct and "and me" is not. You will even sometimes see constructions such as "between him and I," where the "him" is in the right case but the "and I" has been swapped in as the "correct" form.
You will also, of course, have people using the correct form — "Take a picture of my friends and me" — but then thinking it's incorrect. People say things they think are grammatically incorrect all the time. You see, everyone learns grammar, and much of the basic grammar of English is internalized without problem by every native speaker. But there's also quite a lot of grammar that is not automatic or internalized — it's like those rules of good behavior that you have to have drilled into you and that you don't always follow or even learn correctly, like tucking in your shirttails and saying "Excuse me" when you burp.
And, between you and me, I'd have to say this rule is chief among them.