Here are some tactics I am taking:
1) When I enter a new town, check out the equipment and get the best equipment/abilities available for all my characters, unless it is clearly too expensive to be bought. If I'm a little short on cash, go grind a little bit for it.
2) If experience for monsters in an area is still coming at a good pace, grind for a little while and gain some easy levels.
3) If I go into an area and immediately get my ass kicked, don't freak out! I'm probably not meant to be there yet.
4) If I die but almost win, either go grind a little bit, or check to see what attacks the boss or mobs are using. Maybe I just need to go equip fire resistant rings or whatever on everybody.
What kind of tactics do you JRPG veterans use to consistently complete these games?
I disagree with how much focus you put into grinding.
Stat increases from one tier of armor/weapons usually isn't that noticeable. You can skip the grinding if you occasionally skip a tier of armor/weapons and be fine. What you should really be doing is maxing out your inventory on the cheapest healing/mana potions available to always be healed between battles, and a decent amount of expensive heal/mana potions for boss battles.
If enemies in an area are giving you easy xp, the enemies in the next area might give you easy xp too, while letting you make progress. As long as they don't kill you, you can just heal up from those 99x cheap potions you are carrying around.
If you getting your ass kicked in an area means you doing 1 damage while they're wiping your party out in one turn, yeah you're not supposed to be there yet. But if it's clearly pointing you in that direction, you might have just done something wrong. Sometimes you just need to find their elemental weakness, and blast them down with your mage while defending with everyone else. You only have to win once, and after that it's not hard to recreate that win every time you see that enemy after that, unless you're using valuable consumables and taking a ton of turns to win.
If you die but almost win, think about what you could have done differently. Most of the time, your first few turns are inefficient as you feel out the enemy, but once you know the weaknesses and tempo, doing the right thing from the start should be enough to overcome that sliver of damage you missed the first time around.
I only grind if I feel I absolutely need to, which usually means about 2 or 3 grind sessions per game max for me. Waiting until you hit a wall also means the overall time spent grinding is minimal, because you're getting the highest xp possible per grind motivated fight. As long as you're not running from fights you can win, you'll mostly do fine in xp.