When to use at, in and on?

Question

Answer

You might want to learn the prepositions, here is a useful link:
http://www.ego4u.com/en/cram-up/grammar/prepositions

Answer

Right now, I'm at home, in bed and talking on the phone.

Answer

IN/ON/AT

This is a very big question which is impossible to answer here. Here are the commonest uses of these prepositions:

TIME

in the morning/afternoon/evening
in January/February etc
in summer/winter/autumn/spring
in 2012
in the 20th century

on Monday/Tuesday etc
on Monday morning/Tuesday afternoon etc
on my birthday

at night/at the weekend/ at Christmas
(NB this varies according to whether you use GB or US English)

PLACE

The whisky is in the glass
The glass is on the table.

in New York
in Colombia
in Europe

'At' is used for locations where you are interested in the function of the place, rather than the idea of physically 'inside' the place.

At home/work/school

There are also hundreds of other expressions eg 'on my way' which you just have to learn. DON'T try to translate these words directly from Spanish - you should note how English speakers use these words and then copy and learn them. Good luck