Check out one of these sites for more information:
http://bulbapedia.bulbagarden.net/wiki/Main_Page
http://pokemonelite2000.com/
http://www.gamefaqs.com/portable/gbadvance/code/918916.html
http://www.pokemon.com/
http://en.wikipedia.org/wiki/Pok%C3%A9mon
http://www.pokedream.com/
http://www.go-pokemon.com/
http://www.serebii.net/index2.shtml
http://us.codejunkies.com/
Depending on your Trainer ID, Game Version (in your case, Soul Silver), and region (I'm guessing USA), you can give him specific phrases to get 1 of 8 Special Wallpapers for the PC or 1 of 3 eggs.
(See the related link below to get the phrases for your specific version.)
Defeat Flannery of the Lavaridge Gym, and then return to Petalburg City to defeat Norman of the Petalburg Gym.
Route 104, on the way to Petalburg Forest (the route past Petalburg City). He lives in a cabin on a dock on the beach.
In Generation lll games (Emerald, Sapphire, Ruby), Cascoon can only be found in the Petalburg Woods.
After you deafeat your 4th badge from Flannery, Brendan/May will say somthing about battling petalburg citys gym. Go to Petalburg Gym and go through the door until you reach Norman! If you have more Pokemon Questions my profile is Kyogre286.
i can't really remember but did u already get wally?
Where you get slakoth in Pokemon ruby is in the petalburg woods. Trust me
what pokemon?but if its in POKeMON Ruby its either in verdanturf or petalburg
West from Oldale Town.
petalburg gym
in petalburg city
In Petalburg Woods in Pokemon ruby sapphire emerald
in petalburg city
if your just starting he is in petalburg city
Easy 1, Petalburg town...
he is near the woods in petalburg city ;)
You should be able to trade with any compatible Pokemon game, unless you have not arrived in Petalburg City for the first time yet. If you try to trade in Oldale Town right after Professor Birch gives you your Starter Pokemon, the receptionist will tell you the trade center is still undergoing adjustments. So go to Petalburg City and then the receptionist should allow you to trade.
in petalburg city near the Pokemon gym a small cottage