They have a 10% appearance rate when you fish with a Super Rod in any body of water.
luck and a super rod
you cant
Easy! Just trade the red gyarados from soulsilver to diamond.
In Pokemon Diamond Gyarados can be found in almost every body of water using the Super Rod. Alternatively you can catch a Magikarp and level it to 20 for it to evolve into a Gyarados.
The Red Gyarados is a standard pokémon you'll encounter in HeartGold/SoulSilver, but not in Diamond. In Diamond it's a 'normal' shiny pokémon, which means that you need to be very lucky to catch one. You can find Gyarados at many places in Diamond, but the chance of getting a shiny pokémon is 0.0122%.
In Pokémon Diamond, Gyarados will not evolve further.
A red gyarados is a shiny gyarados (however, the Pokemon Company did not call them shiny untill the Unova Region). You can find it wherever you can find a normal gyarados, but your chances to find it are very slim.
A red Gyarados is just a shiny Gyarados. There is no specialty, so just check your Pokédex to see where Gyarados is and start fishing. The chance of a shiny is just too small to look for it purposely. Or you can activate the code for shiny Pokémon and capture Gyarados.
He has a weavile, gyarados, honchkrow, and a crobat in Diamond and Pearl. In the Distortion World, he has a weavile, houndoom, gyarados, crobat and a honchkrow, not necessarily in that order.
only 2 red gyarados and palkia
use pokeradar on a body of water that has lots of gyrados
You may not get a FEEBAS since there are swarms of GYARADOS and WHISCASH.