Get the national dex, deliver the ruby and sapphire to celio (ruby is in mt ember, sapphire is in dotted hole but then in the rocket warehouse), get the hall of fame sticker (four island).
You have to catch a Paris to get tiny mushrooms and a parasect to catch big mushrooms
you have to go into the big forest and around that area there will be a pikachu.
catch all 150 Pokemon and go to celedon city into big building and talk to producer
He's won almost every major European and international trophy.
old lady in the city with big storeyou can get tea in cleadon city near the Pokemon centre
go to the rele big glass buliding in tht town and beat giovani once u get to the rite floor
use your firered or leafgreen and catch parasect it should be holding a big mushroom if not try again and when you get one give it to a Pokemon and transfor it to pal park.
Go east of vermillion city until you find a big building go in go upstairs and talk to the oak aide he will give you the itemfinder.
A good way to beat Mewtwo (Lvl 70 in Soul Silver, assuming you don't want to catch it) is by using your Starter Pokemon (Should be full evolved, high level) and Pokemon with Endevour might be a big help. BEWARE THAT YOU DON'T GET MUCH EXP. FOR THIS. If you want to catch Mewtwo, i would suggest training up a Parasect (Learns Spore and False Swipe) to lower Mewtwo's health, also train up a Sceptile or another Pokemon that can learn False Swipe, so if Parasect faints, another one can take over. Lvl. 70 Strong. I recommend using Timer, Ultra Balls on it.
you get the pokeflute when you rescue mr. fuju on the top floor of that big building with all the mist and ghosts, i don't remember quite what its called but you can use it to catch snorlax...
The duration of The Big Catch is 1200.0 seconds.
Find the oak aide that gives you the itemfinder which should be in the big building east of vermilion city he will ask if you have recorded 30 Pokemon in your pokedex if you did say Yes he will give you the itemfinder.