IN Use 'in' with spaces: * in a room / in a building * in a garden / in a park Use 'in' with bodies of water: * in the water * in the sea * in a river Use 'in' with lines: * in a row / in a line * in a queue AT Use 'at' with places: * at the bus-stop * at the door * at the cinema * at the end of the street Use 'at' with places on a page: * at the top of the page * at the bottom of the page Use 'at' in groups of people: * at the back of the class * at the front of the class

at = you've gone somewhere (to a place) and now you're there gone to work = at work gone to school = at school gone to the park = at the park gone to the shops = at the shops *note* if there is no "to" there is no "at" gone home = home gone downtown = downtown in = inside a place; not outside; you've gone into a place and now you are there in the office; in the park (not outside); in the house; in the garden From these two rules you should be able to derive all the others. Good luck.