Buy about 20 Max Repels and go to the grass north of Pallet Town. Make sure the first Pokemon in your party is below level 50, and just keep running around until you see it.
I caught my Suicune with a level 49 Golbat with Mean Look (so Suicune can't run away).
Raikou is best because entei and suicune are fegget Raikou all the way 2 reasons He is way cooler then Entei and Suicune. Number 2 he could whoop Suicune and Entei in a battle So suicune and entei are good but overall raikou is better
Starter:Charmander-Suicune Squirtle-Raikou Bulbasaur-Entei
Entai = Fire Suicune = Water Raikou = Electricity
You chase Entei and Raikou across Jhoto and you catch Suicune at the top of Cerulean City.
Entei, Suicune, and Raikou are not available in Pokemon Emerald, Ruby or Sapphire. They can be brought into the game by trading.
Entei Raikou
try to answer thoughtful
You can find them anywhere around the routes of kanto so look in the grass.
You get suicune,raikou,or entei depending on your starter pokemon (charmander = suicune squirtle raikou and bulbasaur entei) and you can get mewtwo in cerulean cave
Entei, raikou and suicune
You can't unless you have joto
Lv. 40