Instructions
Go to Goldenrod City and walk to route 34. Search the tall grass for Pokemon. If a male Ralts appears, capture it. Do not catch a female Ralts; it cannot evolve into a Gallade.
Battle with your Ralts until it reaches level 20. At this time, Ralts evolves into its next form, Kirlia.
Obtain one Dawn Stone. In Johto, you can get one of these by winning first place in the Bug Catching contest. You may also find one on Mt. Silver. In Kanto, you are given a Dawn Stone when you reach route 17.
Give the Dawn Stone to Kirlia at any time to evolve it into a Gallade.