How Do I Catch Lugia In Soul Silver?

Well, this is just a suggestion if you don't want to use a master ball.
1. Put it to sleep
2. Paralyze it
3. Freeze it
Hope that helped!

P.S. You can only catch Lugia when you got all 8 gym badges, the silver wing and the bell.

I have no idea but try going to www.gamecheats.com

VERY easy. All you have to do is eventually save or help the 5 Kimono girls, then battle all of them in the Ecruteak City Dance Theater. (They are fairly easy, because they each have only one Pokemon.) You must now have the Silver Wing and the Bell. Then, fly to Olivine City or Cianwood, surf to the islands, use Whirlpool, navigate Whirl Islands, find Lugia, and catch him. I used a Masterball. They never fail.
Hope this helps!

First you will  need to battle the five Kimono girls, then you will go to Cianwood City and surf to the right and use whirlpool where needed to go in the caves and follow the caves and you will find the Kimono girls again and they will let you battle Lugia, make sure you take strong pokemons and if possible put Luigia to sleep or paralyze it

You stock up on pokeballs, greatballs, and ultraballs. Then you go to the whirl islands after you get the silverfeather, and the tide bell. When you find lugia lowwer his life to almost zero and throw your ultraballs if you run out use your greatballs, if those run out, use your pokeballs and maybe confuse lugia and make him fall asleep even.

Jugs get it over with!