Go into Mt. Zublo with equipment that resists or absorbs Fire, and either Fire Magic or Molotovs. You should also have Frost magic. Use Fire magic on Lava Men, just as you would to wake up a Vulcan, but keep casting Fire magic on it. The more you do this, the stronger and more experienced it will become. This will increase their power enough for them to cast Inferno, and their attack is also raised. If you go far enough, you can have the same effect as using Ivory Dice, but it is cheaper. Make sure you have Frost magic to kill them quickly once their power has been boosted. This is important because of the effect this will have on them. It is possible to get up to over 8,000 experience points per character before they get too strong. Be careful to watch how strong they get and stay near an exit. When they become too strong, kill them. Their HP will not increase, everything else seems to. Note: This trick does not work on Vulcans. Once awakened, their experience remains at 900 total, and does not change. However, something similar may work on other monsters with elemental absorbing abilities.
To easily gain experience through fighting and have a good chance of not getting killed, equip a Fire Ring and go to Mt. Zublo. Fight Lava Men and shoot Fire attacks at them, but make sure the person you want to level up is wearing the Fire Ring. After you flame the Lava man for two to three turns, he should use Inferno, healing any damage to the person wearing the Fire Ring, but killing the other two.
Rand: Any people that look like Fahl.
Bow: Anyone that looks like the dog outside the arena betting with a monkey.
Sten: Betting with bow.
Ox: Anyone who looks like the big man from the mines.
Jean: Anyone who looks like the fat frog sleeping in the Wyindia jail.
Ryu: In your party.
Nina: In your party.
Gobi: The orange fish merchants.