First you need to beat the elite 4. After you do, go to the fossil maniac's house(near falabor town)and he will let you go through a tunnel(dont listen to what he says,the tunnel wont collapse,I should know)and catch a ditto.Then go to the daycare center and put in the ditto and the pokemon(magneton,electrod e ect.)and walk around a little bit. Go back and the daycareman saya he found an egg. Walaa!There is your baby pokemon!