Guide to prepositions IN ON AT

Guide to prepositions - in / on / at

​in

use it for enclosed spaces; something that surrounds the subject:
A room, a car, a corridor.

The cat is in a box.

for situations or states: in danger, in good health, in good spirits, in life.

works of fiction

In Harry Potter there are witches and wizards.

Guide to prepositions - in / on / at

​On

used it for technology, digital or analog:
-It's on tv
-Channel on Youtube
-Listened to it on the radio
-Text me on Twitter

used for the top part of a surface

Your PC is on the desk

I dropped my phone on the floor

A picture hanging on the wall

​when talking about occasions, events
On Christmas, on Easter

Guide to prepositions - in / on / at

​At

​used to indicate a location you're in or around
I'm at home / at the company
She's waiting at the hospital

indicates direction
Look at me
Don't yell at your dog

state or occupation

Countries at war

Can't talk now. I'm at a business meeting

​that's all for now.