you can't
Shiny Rayquaza cannot be caught on Pokémon Diamond unless you cheat.
You can trade it from Pokemon Emerald. In Pokemon Emerald, when you find Rayquaza, there is a small chance that it is shiny when you find it. Save the game right before you fight him and keep trying until it turns black. Then catch it and trade it to Pokemon Diamond.
A black Rayquaza is a shiny so you'll have to be very lucky for the Rayquaza you find to be shiny.
You can't find Rayquaza it in pokemon diamond, pearl, and platinum. You just migrate it in Pokemon Emerald, ruby and saphirer
To get a shiny Pokemon try using the poke radar
Once you find a Shiny Pokemon just catch it and it remains Shiny forever.
shiny Pokemon are rare you can find them almost any were but they are super rare
this is a 1 1n 9000 chance, but any wild Pokemon can be shiny. =)
Shiny Pokemon are random, there is no designated place to find them
You can find a Shiny Stone in Route 228 in Pokemon Diamond and Pearl. In Pokemon Platinum, you can also find a Shiny Stone on Iron Island.
you cant find rayquaza on diamond or pearl its from Emreld
No matter what game your playing, shiny Pokemon always appear randomly in the wild.