Basically, the rule is this: You use I when you need a subjective pronoun and you use me when you need an objective pronoun. BUT if you don’t know what I’m taking about, this doesn’t make much sense. So, here’s a little trick: Try deleting Joe from the sentence. Instead, say to yourself, “I went to the store” and “Me went to the store.” I hope you realize that the word you need here is ‘I’. Even when you add Joe back into the equation, you still use I because I is the subject, the person performing the action, along with Joe.

So when do you me? Basically, you use ‘me’ when me is the recipient of some action. For instance, you could say, “Joe gave me money to go to the store.” Me is the recipient of the money Joe gave. Here’s another example: “She fed me grapes.” In this case, ‘me’ is the recipient of the grapes, so it is in the objective position. Now you could turn this around and say, “I ate the grapes that she fed me.” In this case, I is the person who ate the grapes, but me is the person who was fed them.

If this is still confusing, please know that it takes a long time to figure I and me out, and you have made a great start.