It's me or it's I - You and me or You and I
1-it's me or it's I (Which one is grammatically correct)??
2-you and me or you and I (the confusion is same here)??
1 — This one could be confusing. I think it would depend on how it is used. If you are identifying yourself in the third person, I think "it's me" would be used, as in giving someone a choice: "You must choose: it's me or the dog!"
On the other hand, if you are identifying yourself in the first person, it would be used as: "It is I, the author, who writes novels." Notice the contraction "it's" isn't used in this construction.
2 — You and I would be the one to use. The way I was taught was to see if the sentence made sense by dropping the "you and". It would then read, "I ... etc." which would be correct.