I know where you can find a shiny Poliwag!
Surf the water north of Violet City.
Latias is not available in SoulSilver
you find the sihny ston in mewtoo's cave
Unfortunately the chance of finding a shiny Pokemon are quite slim, either your lucky and find one, or you trade with someone who has a shiny you want.
It's an endless amount of Shiny Pokemon, but it is really hard to get or find them.
Yes, you can get a shiny Pokemon out of an egg on any game.
Fight tons of Pokemon or cheat
I went to the Safari Zone and found a Shiny in like a couple minutes
everywhere but very rare
yes... though it is very rare to find one The red Gyarados is part of the game, but I did catch a Shiny Magikarp in Slowpoke Well.
Shiny Poliwag can be anywhere in water, but you would have a very very very little chance of finding it.
yes.zach does
Randomly when you run into a wild Pokemon it may have a different coloration that's a shiny Pokemon. Also a free shiny Pokemon is found in the lake of rage.