Instructions
Train a Pokemon up to Level 45. In "Pokemon Pearl," every Bannette you find in the wild will be Level 50 to Level 54. If you don't have a strong Pokemon, the Bannette will defeat you before you get a chance to capture it. Teach the Pokemon Dark- or Ghost-type moves so you'll have an easier time catching Bannette.
Fly to Solaceon Town, Snowpoint City or Pastoria City. Go to the Poke Mart and purchase 25 Dusk Balls, which will cost you 25,000 Poke Dollars. Dusk Balls have a capture rate of 3.5 at night, which is massive compared to other Pokeballs.
Wait until it is between 8:00 p.m. and 4:00 a.m. in the game. This is nighttime in "Pokemon Pearl." Since Bannette is a Ghost-type Pokemon, you can only capture it at night.
Head to Stark Mountain, Route 225, Route 226 or Route 227. Look for Bannette in the long grass. You have a 20 percent chance of encountering Bannette on Route 225 and Route 226. You only have a 10 percent chance of finding Bannette in Stark Mountain or on Route 227.
Weaken the Bannette to make it easier to catch. Dark- and Ghost-type moves will weaken the Bannette the fastest. Once the Bannette's hit points are low, go to your Bag. Choose a Dusk Ball to try and capture it. You may have to use a couple of Dusk Balls before you catch Bannette.