I've had a request from my friend grrly girl to discuss when to use I in a sentence and when to use me, and also the plurals us and we.
I and me are both pronouns referring to the speaker. No one seems to have any problems deciding which one to use in a sentence when the speaker is the only subject present. From listening to our parents speak, we have learned to say, "I am going to the store", and "Give that to me".
We tend to get into trouble though, when there are two or more subjects present in the sentence. We're not sure whether to use I or me when we are going to the store with someone else, or when we are asking for something.
The easy way to figure out which one is correct is to remove the other person from the sentence. While you might dither over whether it is "Susan and I" or "Susan and me" going to the store, if you temporarily drop Susan from the sentence you will know which pronoun to use. It then becomes easy to say "Susan and I are going to the store" and "Give that to Susan and me."
We and us are the plural pronouns of I and me. If you are in a group of unnamed persons, and you need to know whether to use we or us, drop the rest of the people from the sentence temporarily. If you would use I as the singular pronoun, use we as the plural. If you would use me for the singular, then us is the proper plural. Therefore, you should say, "We are going to the store", and "Give that to us."