in the wild you have a 1/8192 that meens you have a 0.0122% chance which is very low

but its possible its also the same chance if your breeding unless you use the masuda method

you can also in gen IV use the pokeradar 40 times in a row and that increase your chance to 0.5 or 1/2000 chance shinys

now to the masuda method

The key to using the Masuda method is not to breed any two Pokémon, but to breed two Pokémon created in games of different languages-from bulbapedia

the method gives you around a 1/2000 chance i believe it will be in this link probably

masuda method

hope this helps