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 ON Use 'on' with surfaces: * on the ceiling / on the wall / on the floor * on the table Use 'on' with small islands: * I stayed on Maui. Use 'on' with directions: * on the left * on the right * straight on IMPORTANT NOTES In / at / on the corner We say 'in the corner of a room', but 'at the corner (or 'on the corner') of a street' In / at / on the front * We say 'in the front / in the back' of a car * We say 'at the front / at the back' of buildings / groups of people * We say 'on the front / on the back' of a piece of paper

it depends on the sentence..give me example of a sentence,,maybe ill try to explain it the best i can.. :D