Grammar
Style guide 
Prepositions — in and at
Reader's query: Could you please teach me a simple method to remember how and when to use the word in and at appropriately? For example, which of the following sentences are correct?
I live in/at England Garden.
I am in/at the airport.
I am waiting for you at/in the lobby.
at
We use at for specific addresses.
I live at England Garden.
We use at with places.
At the cinema, at the corner, at the airport, at the lobby.
in
We use in for the names of towns, states, countries etc.
I live in Sydney.
We use in with spaces.
In a room, in the garden, in the lobby, in the park, in the airport.
So I would say:
I live at England Garden.
I am in/at the airport depending on where I was at the airport.*
I am at/in the lobby. I think you can use either in or at.
* In indicates you are inside the airport, whereas with at you could be standing outside the airport.
References: http://grammar.ccc.commnet.edu/grammar/prepositions.htm http://esl.about.com/library/grammar/blgr_prep1.htm
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