Link?
http://www.serebii.net/games/shiny.shtml
In the fourth generation, a variety of things have changed in order to allow for the obtaining of Shiny Pokémon. First is a method commonly known as the Masuda Method, named after the game developer and the person who revealed it; Junichi Masuda. This method has you breed two Pokémon. However, one of the Pokémon must be of a different nationality than your game (such as a Japanese Pokémon on an English game). This will lower the chances of hatching a shiny Pokémon from 1 in 8,192 to 1 in 2,048 cutting it by 75% in Generation IV. However, in Generation V, it is boosted even further from 1 in 8,192 to 1 in 1,365.3. Generation VI has increased the likelihood even further, with the rate being reduced even further.