A grammar thread because I guess we need this. RT to save a poor soul from my unrelenting ridicule.

You're = you + are

WHEN TO USE IT:
If you instead use "you are" and the sentence still makes sense, use it. "You're a bad person."

WHEN NOT TO USE IT:
"Is that you're car?"

Your = you possess a thing

WHEN TO USE IT:
"Your wallpaper choice is heinous."

WHEN NOT TO USE IT:
"tfw your breathing lmaoooooo"

Their = they possess a thing (aka the pronoun version)

WHEN TO USE IT:
"Their website is gonna get shut down for hosting illegal copies of Apple operating systems."

WHEN NOT TO USE IT:

"Look over their, it's the dumbass who hosted illegal copies of operating systems!"

They're = they + are

WHEN TO USE IT:
If you instead use "they are" and the sentence still makes sense, use it.

WHEN NOT TO USE IT:
"They're t-shirt is stained and I can smell it from here. It's disgusting."

There = somewhere

WHEN TO USE IT:
"Look over there, it's the dumbass who hosted illegal copies of operating systems!" or "There, I told you it would work." or "Hey there!"

It's = it + is OR it + has

WHEN TO USE IT:
If you instead use "it is/has" and the sentence still makes sense, use it. "It's been 87 years..."

WHEN NOT TO USE IT:
"It's AC unit fell out the window and killed a guy. It was hilarious, did I send you the video link?"

Its = It possess something

WHEN TO USE IT:
"Its lineup features the Camry, Corolla, and some boat engines I think"

WHEN NOT TO USE IT:
"Its Wednesday, my dudes. aaaAAAAAAAAAA"

To: usually involves something/someone moving OR location.

WHEN TO USE IT:
"We didn't come to a complete stop before dumping the body" or "When to use it"

WHEN NOT TO USE IT:
"To little, to late."

Too: usually involves something additional or excessive

WHEN TO USE IT:
"Too little, too late."

WHEN NOT TO USE IT:
"I'm not going back too jail, ya sons a bitches."

Two: literally just the number 2

WHEN TO USE IT:
Slot in the number 2. If the sentence makes sense, use it.

COULD'VE = could + have

WHEN TO USE IT:
"You could've had a bad bitch, Malcom Middle."

WHEN NOT TO USE IT:
Up to you, really. Use both "could've" or "could have" for all I care. It's your life.

COULD OF = what stupid people think "could've" means

WHEN TO USE IT:
Never, "could have" isn't a phrase.

WHEN NOT TO USE IT:
All of the time, "could have" isn't a phrase.

LIE/LYING = to recline. you don't need to do anything for someone/something to lie down.

"I'm lying down for 45 to an hour, don't talk near me or so help me god I will destroy you"

LAY/LAYING = to place down. In order for something to be laid down, you need to take action.

"I laid the bed sheet down to discover the bloodstains from my past marriage had yet to wash out."

The educational system has failed you if you needed this refresher. You should file a lawsuit.