Your vs You're
From TEFL World Wiki
Confusing Your and You're is a common mistake made by learners and native speakers alike. This article explains the difference between them and when to use them.
Difference
Your is a possesive adjective which shows that something belongs to someone or a group of people.
In the singular, it is used when speaking to one person:
Where is my coat?
You put your coat over there.
In the plural, it is used when speaking to a group of people.
Ok everyone, make sure you pick up your bags and put them on the coach.
Meanwhile, you're is a contraction of you are.
You're going to be the first to arrive.
Teaching the Difference
If a student has a problem choosing which one to use, simply explain to them that they need to expand the contraction and see if the sentence still makes sense.
Thus,
* You're car is really dirty!
becomes:
* You are car is really dirty!
which is obviously wrong.
