Just like uhm, the Gym's weaknesses or something xD
I have no idea what to type... I've got it!
The kanto gyms:
Brock: Hydro pump them to death.
Misty: Thunder, or a strong grass move.
Lt. Surge: Earthquake to death.
Erika: Fireblast, flamethrower, OR Aeroblast.
Sabrina: Any dark move, preferably Bite.
Koga: Psychic, or Psybeam to death.
Blaine: Hydro pump them to death.
Giovanni: Psychic, and some other moves.