everywhere but very rare
Yes, you can get a shiny Pokemon out of an egg on any game.
Fight tons of Pokemon or cheat
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.
Keep walking in tall grass.
Latias is not available in SoulSilver
pogi
You transfer it from Heart Gold or Soul Silver.
there isn't one.
it is very hard. you have to get very lucky or use a cheat
It evolves by using a Shiny Stone
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.