1. Get a Ditto and put him the Pokemon Daycare.
2. pick the Pokemon you want make an egg of and put it in the daycare.
3. Go to the bike road and go up and down by clicking up repeatedly quickly
4. go back get your egg
5. Have a Pokemon with magma amour (slugma will likely have it)
6. go back to the bike road and do that again it will hatch in no time
7. put the Pokemon that came out of the egg in the day care and go back to cycling road they will level up real quick for the first 10-15 levels
8. For those of you who beat the elete four go to where the battle tower areas are and equip your Pokemon with EXP-share pace him/her in the first slot then switch out Pokemon with that Pokemon and beat them this will level them up quickly