"I" is the subject of a sentence, while "me" is the object, meaning that you should use "I" if you are the one acting, while "me" is the word to use when an action is done to you.
Ex: I ate the fish.
Ex: The fish ate me.
However, since not all sentences are this simple, there are some places where you might still get confused.
Below are some common stumbling blocks with "I" and "me."
The Rules
Use I, along with other subjective pronouns such as we, he, she, you, and they, when the pronoun is the subject of a verb:
EX: Jim and I are going out for dinner.
Use me, along with other objective pronouns such as us, him, her, you, and them, when the pronoun is the object of a verb:
EX: The cat followed Meredith and me to the kitchen.
Use me, along with other objective pronouns such as us, him, her, you, and them, when the pronoun is the object of a preposition:
EX: Pam spent the entire evening with Jim and me.
The Trick
There is an easy way to check if you’ve used the correct pronoun. All you need to do is remove the additional noun and see if the sentence reads properly:
Jim and I are going out for dinner. (In this example, the “to be” verb are must be switched with am for the sentence to make sense.)
The cat followed Meredith and me to the kitchen.
Pam spent the entire evening with Jim and me.