Since I've seen a lot of people do these mistakes in their stories, I'll help a little out.
A lot of people use Your AS You're. Which is incorrect! Your is possessive, and You're is a combination of two word. You and are. Your is used when a person (who you would adresse with you) possesses an object. You're is a state of be. That person IS something.
Examples:
YOUR book looks so cool!
YOU'RE that famous guy, right?
Also, what I have noticed too is THEIR and THEY'RE. Which is the same thing as above but with different pronouns!
Examples:
THEIR umbrella is gone!
THEY'RE so cool!
If you have any questions, feel free to ask