Things You'll Need
Instructions
Catch a Poliwhirl or a Poliwag. Poliwag is very common and can be found in random encounters initiated by fishing and surfing. Poliwhirl is less common, but it can be found the same way.
Fight using the Poliwag and raise it to level 25, which will cause it to evolve into Poliwhirl.
Equip the Poliwhirl with a King's Rock. This can be found in "SoulSilver" in the Slowpoke well of the Johto region. You need a Pokemon that knows Surf to reach this area. A King's Rock can also be traded from another game or purchased from the Pokeathlon Dome once you have the National Dex, a type of Pokedex.
Trade the Poliwhirl to another Pokemon video game, such as "Pokemon HeartGold" or even a second copy of "SoulSilver." Poliwhirl will evolve into Politoed. Because Nintendo DS trading can be done over the Internet, it is much more practical than in older versions, which required two Game Boys, multiple game cardtriges and a cable that could link the systems together.