If you ever happen to see it but forget to catch it or you own a suicune thanks to a friend giving it to you you can use the pokedex to check where it is but it ALWAYS moves so the best spot to be in is at route 1.
There are about five you can catch or six 1 Lugia, get silver wing 2 Ho-oh, get Rainbow Wing 3 Raikou, track it down 4 Suicune, track it down 5 Entei, track it down 6 Celebi, only through an Nintendo Event Suicune, Raikou, and Entei you have to be careful with you kill them they are gone. Try and save when you are in there area. Also a Pokemon that knows Sleeping Powder would be good. Good Luck!
No.
You have to beat the elite four and catch Mewtwo. If you started with Charmander, you will be able to catch suicune. If you start with bulbasaur, you will catch the fire type Entei. If you start with Squirtle, you will catch the eletric type Raikou. All have the same idea. Suicune/Raikou/Entei will be running around so you will have to meet up with them and track them down in your pokedex. If you use bike or Fly, they will be scared away. Use your Master Ball on them. Good Luck!
there is no real location.It is like catching latios and latias in emerald. it will just appear in your path sometimes. you use the pokedex to track it down. i found it in the sea.
zapdos, at the power plant down from the rock tunnel you have to surf there
Its from the left of Viridian City down route 22.
Entei can be found in Pokemon LeafGreen roaming Kanto if the player selected Bulbasaur as his starter pokemon. Entei is a pokemon created by Ho-oh said to represent the fire that burnt down the Brass tower.
At The Ship In vermilion city down from Misty's gym
go down and then left from fushia through the seafoam islands
It is on six island.Go left,down and you will get to water path.
well firered and leafgreen have SOME different Pokemon so you can get those Pokemon from leafgreen. so here is the site that list the different Pokemon. just scroll down to the chart... http://bulbapedia.bulbagarden.net/wiki/Pok%C3%A9mon_FireRed_and_LeafGreen_Versions
you go down to the house next to the Pokemon center and inside is this guy, talk to him and he will give a secret potion.