Use a master ball.
You can only get Suicune if your starter was Charmander. After you defeat the Elite Four, it will appear in tall grass at a random time and location. It is best to catch it with a Master Ball, or at least have a Pokemon with a trapping move, as it will always try to run.
net ball, fast ball
This is VERY debatable. Most say Mewtwo, Mew, Raikou, Entei, Suicune.
the best pokeball to catch suicune with is a great ball
Other than the masterball try using a lot of ultra balls.
It actually doesn't matter what level your party is to catch suicune the best way to catch is to use the masterball but if you don't have it have a Marowak or Scyther at level 100 use False Swipe to get Suicune's HP to 1 it will run find it again and use sleep powder or hypnosis on it start throwing ultra balls to catch it.
The best ball to catch suicune with would probably be the level ball if you have lots of high level pokemon. you can get the level ball from Kurt in azelea town using apricorns. ( i don't know what color apricorn it is, so your on your own for that.) Besides that, i caught my suicune with a ultra ball. so jus buy a lot of ultra balls if anything. :)
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.
First you have to find it which you can find it pretty much anywhere the best route is Route 1. Use a masterball on it to easily capture.
bulbasaur, squirtle and charmander are all great to start with, but i find charmander the strongest. charmander is also the best for obtaining suicune
I don't understand your question, so I'll answer it to the best of my knowledge. There is Ho-Oh, Lugia, Suicune, Entei, and Raikou...I'm not sure if you can catch Articuno, Moltres, and Zapdos though...
go to the rainbow islands(islands 5,6 nd 7) and capture all the pokemons......!! I knoe the best pokemons for you to catch.....mewtow in cerulean cave...you have got to surf for that.....and suicune, entei or raiku depending on which your starter Pokemon is.......entai for bulbasaur..suicune for charmendar.....and raiku for squirtle!