What are the best ways to beat the elite four in Pearl?

If you don't want to grind your Pokemons levels, catch Palkia, and then at least two of the three lake Pokemon. Your starting Pokemon (Torterra, Infernape, or Empoleon) should be pretty high-level by now, 55-60. Then, get as much money as you can and buy 40 hyper potions, ten full restores, 15 super potions, 20-30 revives, 10 full heals, and 5 of each of the status-removing sprays(antidote, paralyze heal, etc.). If you have any useful TMs, put them onto the four best Pokemon. Fill your extra two Pokemon slots with Pokemon from the base of the waterfall outside the building. Heal between battles.