So, as to the grammar of you're and your:
You're is literally just you are with a apostrophe in the place of the "a" and the space squeezed out of it. You use it when you are telling someone about themselves. "You are going to be on the moon tomorrow" is the equivalent of "You're going to be on the moon tomorrow." It's just slightly less formal and generally used for dialogue.
Your is the possessive form of you. You use it when you're talking about the person owning something. "This is your monkey."
Now a review:
You're = you are
your = possessive
If you have trouble, just remember that you are is like I am, both can be shortened by an apostrophe; I'm and you're.
Your is like my. They are both speaking of possession.
Also, say it out loud. If the sentence should say you are, add an apostrophe.
I'm perfectly willing to answer questions, if needed.