There are different rules for using I or me in a sentence, depending on whether you are writing in first person or third person. In first person, you would use I when you are the subject of the sentence and me when you are the object. For example, "I went to the store" and "The store clerk helped me." In third person, you would use the person's name as the subject and me as the object. For example, "John went to the store" and "The store clerk helped me."
