In general, we use:

at for a POINT
in for an ENCLOSED SPACE
on for a SURFACE

Use AT

a. with places on a page:
at the bottom of the page

b. in groups of people:
at the back of the class
at the front of the class

c. places/point:

at the bus-stop
at the door

ON

Use 'on' with surfaces:
on the ceiling / on the wall / on the floor
on the table

Use 'on' with small islands:
I stayed on Maui.

Use 'on' with directions:

on the left/on the right
straight on

IMPORTANT NOTES

In / at / on the corner
We say 'in the corner of a room', but 'at the corner (or 'on the corner') of a street'

In / at / on the front
We say 'in the front / in the back' of a car
We say 'at the front / at the back' of buildings / groups of people
We say 'on the front / on the back' of a piece of paper

Notice the use of the prepositions of place at, in and on in these standard expressions:



Activity

1. I am ____ work.
2. We are sitting ____ the park. It is a nice day.
3. My car is parked ____ the parking lot.
4. Our house is ____ the end of the street.
5. My sister lives ____ the 6th floor.
6. The books are ____ the bag.
7. The books are ____ the table.
8. There are a lot of books ____ the library.
9. I called their house, but nobody is ____ home.
10. There is a beautiful picture ____ the wall.