at/in and to

The difference

At and in are generally used for position (for the difference, (see here); to is used for movement or direction. Compare:

• He works at the market.
  He gets to the market by bike.
• My father lives in Canada.
  I go to Canada to see him whenever I can.

Expressions of purpose

If we mention the purpose of a movement before we mention the destination, we usually use at/in before the place. Compare:

• Let’s go to Marcel’s for coffee.
  Let’s go and have coffee at Marcel’s. (not Let’s go and have coffee to Marcel’s.)
• I went to Canada to see my father.
  I went to see my father in Canada. (not I went to see my father to Canada.)

Targets

After some verbs, at is used with the ‘target’ of a perception or non-verbal communication. Common examples are look, smile, wave, frown.

• Why are you looking at her like that?
• Because she smiled at me.

At is also used after some verbs referring to attacks or aggressive behaviour. Common examples are shoot, laugh, throw, shout and point.

• It’s a strange feeling to have somebody shoot at you.
• If you can’t laugh at yourself, who can you laugh at?
• Stop throwing stones at the cat, darling.
• You don’t need to shout at me.
• In my dream, everybody was pointing at me and laughing.

Throw to, shout to and point to are used when there is no idea of attack.

• Please do not throw food to the animals.
• Could you shout to Jake and tell him it’s breakfast time?
• ‘The train’s late again,’ she said, pointing to the timetable.

Arrive is generally followed by at or in; never by to.

• We should arrive at Pat’s in time for lunch. (not … arrive to Pat’s …)
• When did you arrive in New Zealand? (not … to New Zealand?)

note

For in and into, (see here).