After you defeat Misty, You can go catch suicune by Bill`s house.
route 25
You can go and challenge other Gym Leaders in the Kanto region, such as Brock.
Once you fixed the Power Plant, go to the end of Route 25. Talk to Misty and she'll return to the gym. Then you can beat her. (She uses water Pokemon so I suggest you use grass or electric Pokemon.)
misty will be a gym leader in HeartGold and SoulSilver
you go to the power plant talk to everybody there go to mistys gym after that and there will be a man in black there beat him in a battle and then go to the side of house there you will see misty.
Misty is at the Cerulean Cape. It's close to Cerulean City.
Misty has a 49 Golduck 49 Quasire 52 lapras and 54 starmie
She's at the end of route 25
top of rout rout 25 =]
misty
During your first battle against Misty in Pokémon SoulSilver, you can use Electric attacs against all of her Pokémon except for Quagsire. You need to use a Grass attack or a Flying-type attack against Quagsire.
Route 25, near Bills house.