well you chase suicune around and i will tell you the order you have to go
North of cianwood city
route 42 outside mt.Morter
in vermillion city
route 14
after misty has returned to her gym beat her and go to outside of bill's house on route 25 this is where you battle suicune and if you defeat it just beat the elite for again (lance)
Chat with our AI personalities
After Mount Mortar, Suicune will travel to Kanto where you will see it Vermillion City shortly after you arrive on the SS Aqua.
after you have defeated all 16 gyms go to were you found misty and his boy and suicune will be there.
The pokemon Suicune can be found on Route 25 of the Johto Region. If the pokemon faints or runs away during battle, it is possible to have a rematch at the Burned Tower in Ecruteak City.
Other than the masterball try using a lot of ultra balls.
The Shiny Suicune was a game stop event held before Pokemon black and whiter where releases. You had to get either suicune riakou or entei at the event of your Pokemon Pearl/diamond/platinum/soul silver/ or heart gold version, and then transfer them to your Pokemon black/white version.