Originally Posted by K R Y
Use 'then' when in relation to time. 'Than' in relation to comparison.
'Your' is possessive. 'You're' is descriptive.
Your keys. Your house. Your mother.
You're a twat. You're going to be a twat when you grow up.
Throw em together = You're your mothers twat
I always found when I was younger the best way to remember it was that 'you're is short for 'you are'