Well, there are the fixed shinies (Red Gyarados in SS/HG, Gible/Drantini and Haxorus on BW2) but I doubt you are interested in those.
So I would suggest using the Masuda method. Breeding two Pokemons from different countries, the chance of getting a shiny increases to 1/1366 from 1/8192. The chances are still pretty dim though.
Another way to get shinies easier is to get the Shiny Charm in BW2. It increases the chance of getting a Shiny in the wild to 1/2730 and slightly improves the Masuda Method, to 1/1024. However, you get the Shiny Charm by completing the National Dex, so it is quite difficult.
But despite all this, the one thing you need is patience. The very best chance of getting one will be 1/1024, a very small chance. Time is key, play a lot, and sooner or later you will find your Shiny!