Instructions
Take your two Pokemon to the Daycare Center. The location of the Daycare Center depends on which game you have. In "Pokemon Diamond," "Pokemon Pearl" and "Pokemon Platinum," the Daycare Center in near Solaceon Town. In "Pokemon HeartGold" and "Pokemon SoulSilver," the Daycare Center is just south of Goldenrod City.
Deposit both of the Pokemon into the Daycare Center. If you have a female Lucario, you will need another Pokemon from either the Ground group or the Human Shape group. You can also use a Ditto. If you have a male Lucario, you can only use a Ditto. Talk to the Daycare Center owner after you have deposited the Pokemon to find out whether they will mate. As long as he does not say, "The two prefer to play with other Pokémon more than with each other," the two Pokemon will eventually produce an egg.
Walk around until you receive a call from the Daycare Center owner. Depending on what the Daycare Center owner said about the two Pokemon, this can take a few seconds to several minutes. The owner's statement determines the chance of the Pokemon producing an egg after every 256 steps. If the owner says, "The two seem to get along very well," you will have a 70 percent chance of producing an egg every 256 steps. If the owner says, "The two don't seem to like each other," you will have a 20 percent chance of producing an egg. If he says anything else, you will have a 50 percent chance of producing an egg. Once the owner calls you back, retrieve the egg from him.
Walk around until the egg hatches. This can take up to 6,400 steps. If you have a Pokemon with Flame Body in your party, the hatching time will be reduced by half.