How to get Lugia and Ho-oh in Pokemon D/P <official>
First you must have:
For Ho-oh you need:
Pokemon Ruby, Sapphire, Firered, Leafgreen or Emerald game pak
Gamecube/Gameboy Link Cable
You must have beaten story mode on Colloseum
You must have beaten The Elite Four on Pokemon Game Paks
You must have the National Dex on Pokemon Diamond or Pearl
First, on Colloseum go to Mt. Battle with your greatest team. (bring your master ball if you still have it or ultra
Then, beat all 100 trainers.
After that, Ho-oh will appear for you to catch.
After catching Ho-oh, trade it into your game pak.
Then, put your game pak in the second slot of your DS.
Migrate Ho-oh (make sure ho-oh has no HM moves) and five other pokemon.
Ta-da you have Ho-oh!
If you have Emerald, clone the Ho-oh in the Battle Tower. (Helping links at the bottom.)
So you can have a Ho-oh army!!