look for it on your pokedex then fly to that place have a reasonable amount of pokeballs on you try not to go through any buildings because that wil make suicune move to another place aslo make sure your starter is charmander make sure use meen look or have a wobeffet

but flying also makes suicune move

oh yeah sorry

ok you have to get your starter pokemon charmander that when you beat the game he will appear somewhere i suggest getting 20 max repels and walking with a pokemon at level 40 and have quick attack or really high speed once you find him look in one spot go into a house he will always change areas so its good to just go in and out the house/pokemon center then check where he is then go to him seduce him and catch him