* "At" is used when referring to a specific location:
* "We'll have the meeting at the conference room."
* "I'll meet you at the coffee shop."
* "In" is used when referring to a more general location or a place that's not a specific building:
* "The meeting will be in New York."
* "We'll be meeting in the city center."
* "I'll meet you in the afternoon."
In summary:
* If you're specifying a place, use "at."
* If you're specifying a broader location or time frame, use "in."