It should go without saying, but ALWAYS have at least one Transfer Potion on you at all times, you never know when things will get hairy and you'll need to jump back to into town.
Transfer Potions can typically be found often on the first floor, in the first section beyond the entrance door, around the corner in that first section, or you can always buy one at Smiley's Shop.
NEVER use the "Flee Together" option if you can possibly avoid it, because if the escape fails, then your entire party is vulnerable to enemy attack, and you'll be especially screwed if your opponents choose to use the "Rush" action on you.
Instead, use the "Front Guard" allied action (if your opponents are primarily fighters) or the "Spell Guard" allied action (if your opponents are primarily spellcasters), then have your remaining characters individually use their "Flee" option, that way, you stand a better chance of escaping, while at the same time, safeguarding your party until you succeed in said escape.
While at Vigger's shop, if you have at least one spell material on you, you can still click on and preview what materials are needed for spells that are in gray, that way, you can either save up the appropriate materials, or plan your shopping list at the materials shop on the first floor of the labyrinth when it opens up.
If you've obtained a stronger weapon or armor that requires your character to be of evil alignment to equip, fear not, either release an item's SP to turn your character evil, or fight a friendly group of enemies, then you can easily turn your character back to a good alignment simply by not fighting a few groups of friendly enemies.
Sometimes having one of your characters get possessed by the reaper is necessary for finding secret doors.
Two such occasions are in the first hallway of the second floor (Old Jail) and one of the far eastern sections of the sixth floor (Moldy Fort).
You can tell when you're near a secret door when you hear a heartbeat and your controller starts vibrating.
If you want some free appraisals, you're pretty much safe equipping any ??? item you get from the first floor to see what it is, but I wouldn't recommend doing this with items from any other floor, as you might get cursed.
Finally, opponents cannot touch you if you're standing in a teleport circle.
Not so much a tip or a cheat as it is a time-saver, especially if you're getting tired of looking at his ugly mug, but whenever the cut-scene starts that heralds the arrival of the reaper, you can simply pause and un-pause the game to skip the cut-scene.
This is the only cut-scene or sequence I've found this trick to work on, however.
To disarm traps easily, all you need to do is pause the game when the trap pattern pops up. Then analyze the pattern, unpause, and quickly punch it in.
Can't afford that new item? No problem. Make money the easy way. All you have to do is go to guild and create a new character and put him on your team. After doing this remove their items and dismiss them. And there you go you have a new set of items to sell. Sure its cold, but thats what they get for trusting a perfect stranger with their stuff.
I don't know if others thought about this before me ... It took me one year to realize this... (note I own the Pal version) bust just as soon as you can create new allies at the Guild (after defeating Virgo for the first time) you can become extra rich, I created new characters put them in my party and after having sold all of their equipment I obliterated them and create new ones, I got already 100.000 by the time I got in the 2nd floor...
If you take a material or items to the shopkeeper in the Labyrinth then you can return "anytime after" and buy it...for example the broken sword, dragon heart, slime jelly, giant guts, cocoon, wyvern eyeball...etc.