You're, it's, and there...these are three of the most troublesome words in the English language. It's because they have siblings who sound just like them, even though their meanings are very different.
Here's my breakdown on these tricksters:
Your (possessive - it's yours) umbrella is going to be helpful if you're (you are) out in the rain. Your must be followed by a noun - your what? You're must be replaceable with 'you are.'
2. IT'S vs. ITS
It's (it is) going to rain today. The sky is going to open up its clouds (possessive - the clouds belong to the sky.) If you can replace it's with 'it is', use it's. If you can't, use its.
3. THEY'RE, THEIR, and THERE
They're (they are) going to take their (possessive - always followed by a noun) umbrellas over there (a place opposite of here.) They're must be replaceable with 'they are.' Their always means belonging to them. If it's not either one of these, it's there.
Got it? You can bookmark this page and use it as a cheat sheet. I'll never tell.