"You and "I is used as the subject of a sentence: You and I went to the movies.
"You and me" is used as the object: My sister went to the movies with you and me.
To figure out which you should use, eliminate "you."
You wouldn't say "My sister went to the movies with I, " or "Me went to the movies."
Subject pronouns: I, you, he, she, it, we, they, who
Object pronouns: me, you, him, her, it, us, them, whom