Lead with a strong Fighting-type for Persian
Use Lucario, Machamp, Conkeldurr, Terrakion, or Keldeo if available
Shield the first charged move from Persian if needed
Save shields for Giovanni’s second and third Pokémon
Bring a Water-, Grass-, or Ice-type for Nidoking, Rhyperior, or Kingdra
Bring an Electric-, Rock-, or Ice-type for Ho-Oh
Bring a Fairy-, Dragon-, or Ice-type for Palkia
Bring a Grass-, Ice-, or Water-type for Groudon
Bring a Ground-, Rock-, or Water-type for Heatran
Bring a Dark-, Ghost-, or Bug-type for Cresselia
Bring a strong counter to Giovanni’s current Shadow Legendary
Use fast-charging charged moves to burn shields quickly
Use Pokémon with spammy charged moves like Power-Up Punch, Cross Chop, Aqua Tail, or Weather Ball
Keep your first slot as a Persian counter
Keep your second slot as a flexible mid-game counter
Keep your third slot as your best answer to the Shadow Legendary
Re-enter with the same team if you lose to learn the lineup
Adjust counters after seeing Giovanni’s current team
Use high-level, powered-up Pokémon with good IVs
Use type advantage and shield pressure over raw CP alone