To Ricardo and all the people who - myself included - think that prepositions suck!
1- AT
I have to wake up tomorrow at 6:00Note: Activity + AT ..........but
Saying the time: No Preposition
EX: We're going to be late! The movie starts at 8:00 and it's 7:45 now.
At the zoo, at the restaurant, at the theater, at the supermarket, etc.
Exceptions: At church, at home, at work, at school (without THE)
He's at work today. 
They're singing at church now.
Ted decided to stay at home because he's sick.
She was at school yesterday.
Daisy likes to study at the library
Andrea lives at 1313, Happy Street
AT + number but
Andrea lives on Happy Street
More examples:
At the bus stop At the door
At the traffic lights At her desk
Longer holidays such as:
(AT) Christmas, but on Christmas day,
(AT) Easter, (AT) Carnival
For things that have a beginning and an end - things you can measure:
At the end of the film, At the beginning of the class, etc.
Also: At night
