Take Advantage of Rush and Ambush: Use the Rush feature to quickly finish battles and take advantage of ambushing enemies for extra experience
Equip the Proper Persona: Equip Personas that are strong against the enemies you are facing to gain more experience.
Explore Tartarus: Revisit floor sections in Tartarus that you have already completed to farm experience.
Exploit Weaknesses and All-Out Attacks: Aim for enemy weaknesses, trigger All-Out Attacks, and take advantage of Shuffle Times to look for Wand cards, which can help you level up quickly.
Balance Your Party: Balance your party to distribute experience evenly and focus on leveling up weaker characters by not filling your party with only powerful characters.