Another combat tip for MM2:
Fire and Cold are resisted by many (perhaps even most; it certainly feels that way sometimes) enemies, including some you wouldn't expect to resist them (in particular, undead tend to be immune to fire, which is the opposite of how most RPGs with elemental attacks and undead behave); as a result, spells of those elements tend to only be useful in special situations.
Electricity and Acid, on the other hand, are resisted far less often. If you don't know about the enemy's resistance, using spells of these elements is a reasonably safe option. For this reason, Lightning Bolt can be your main attack spell until you get Disintegration, and Mega Volts is generally more useful than Inferno, with Dancing Sword best used only when electricity doesn't work.
Of course, non-elemental spells with fixed costs tend to be the best, like Disintegration, Implosion, and Deadly Swarm (Cleric).
Also:
Casting Turn Undead will cause Holy Word to fail if you try casting it later in the same battle, so the strategy of casting Turn Undead, then using Holy Word when that fails, will not work. (With that said, Holy Word does not age the caster in the DOS version of 2.)
Divine Intervention can only be used once per battle, and only during battle, but if you have high HP (either temporarily or permanently) it's worth the aging.
Rejuvenate is best cast after you save the game by entering the inn, but before you turn off the game; if it succeeds, save and try again, and if it fails, just turn off the game. Note that, if this spell would reduce your age below 0, it *will* backfire.
A character who is 80 or more years old may die when you rest, but I believe the character is not otherwise at risk (if you're clever with the fountains, you might even be able to avoid resting entirely).
Similarly, spells only wear off when you rest; you can go days without your spells wearing off. Also, hirelings only charge money when you rest with them in your party (the game won't let you rest if you don't have enough), and IIRC food is only consumed when you rest.
I have never seen Recharge Item or Duplication destroy the item; Recharge Item will not work on items with 0 charges (but you can use Uncurse Item (which doesn't work as presumably intended) to give it a charge), and Duplication will only work for items that can be randomly dropped by enemies.
Frenzy is bugged; it doesn't permanently lower Endurance, and it makes your offensive spells always succeed. This is game-breaking enough that I would consider it an exploit (especially since Finger of Death exists).
Sarisio: Also MM games have very high level caps, so if you make some mistake in party development you can always fix it by gaining few more levels.
That's not true in MM4, where you can train only up to level 20, and where the highest attainable level is 23 with permanent boosts, or 33 with temporary boosts. (This is for MM4 alone; traveling to the Darkside (MM5) will let you reach much higher levels.)
Also, I believe that in MM1, reaching really high levels is not feasible, as enemies don't give that much XP.
With that said, both of these games pre-date the MM6 skill point system, so there are no choices you could make in party development (except for choosing your initial classes) that could be mistakes. (That's one reason I think I prefer not to have a skill point system; no mistakes to make.)