If you'd asked me last year what it would take to beat a game really fast I'd have told you things like learning all of the maps. Knowing where all the enemies are, and how to react to them. If it's a game with RPG elements then knowing what treasures to run to and which ones to skip. If you need to gain extra levels or not. I'd probably think to mention something like working out enemy weak points (especially if I was thinking about a Mega Man game, where using the right weapon on each boss can really speed things up).
I probably wouldn't have thought about finding weird bugs and abusing the living daylights out of them. I probably wouldn't have even mentioned something like a 'damage boost' which is where you intentionally take damage in a platformer in order to gain a bit of invincibility and get launched a little bit in the right direction. There are spots in Chip & Dale's Rescue Rangers where you go faster because there are enemies in your way and you can jump into them at the right spot to boost yourself the way you want to go. It's a little crazy, but it's faster, and that's all that matters!
All of the stuff I mentioned at the start is really important too. You're not going to get anywhere fast without a proper plan and a lot of practice inputting the exact right commands at the right times. But the people who go the next step are going to have a higher ceiling for how fast they can go because they're squeezing extra speed out of more elements.
Which means if I want to be really fast at Final Fantasy Mystic Quest I need to know what glitches exist in the game. This is possibly more important than just getting good at the menus and knowing what spells to use when because some games can have glitches that fundamentally alter the way you play the game. 3D platformers and adventure games are notorious for having out of bounds glitches where you can jump or clip through a wall and skip entire parts of the game. Getting really good at a Zelda boss fight that no one else fights because you can skip it isn't going to be a very good use of your time! So I've been doing some searching to find out what glitches are known for Mystic Quest...
First there are glitches that no one seems to be using and that seem pretty worthless. There are a couple glitches with battlegrounds such that you can either gain an extra level prematurely or can set it up to get infinite fights. These could be useful if you desperately needed to hit one specific level, or if you needed access to a large number of quick fights to grind up experience or cash. Mystic Quest is easy enough (thanks to having a high level buddy) that neither of those things feel useful at all.
There's also a glitch where one of your buddies can randomly cast a powerful spell she doesn't know, but only if she's out of mana for a powerful spell she does know. Since this occurs after you can buy a large number of seeds (and hence have essentially infinite spell charges) it probably isn't much use. I'm going to be keeping my eye on it because maybe there are enemies weak to aero or something and it's actually faster to keep her going at no spell charges? I doubt it, but it's going to be in the back of my mind.
Then we have some glitches that are used in current speed runs. There's a bug where the life spell kills off non-zombie enemies instead of zombie enemies. This is more of a thematic glitch I guess since I was planning on testing every enemy anyway to see which ones could be lifed to death.
There's a brutally powerful overflow glitch where enemy health is stored in a 16 bit field so if you can put them over 65535 health it wraps back around. Because the mechanic for the cure spell is percentage of max health based (at level 24 you heal your target for ~91% of their max health) and the end boss has 40k health you can abuse this glitch to kill him in 3 rounds mostly with the cure spell. I don't think any other enemy in the game has enough max health to hit the glitch threshold but it's certainly used to trivialize the final boss.
There's a weird bug where once you get the 3rd bomb weapon you can start throwing bombs. If you run out of bombs you still have the 'throw bomb' button, but it glitches out to be 'repeat last action' instead of 'throw bomb'. There's one dungeon where the 'last action' can be to ride a bucket down to the next floor of the dungeon. Run out of bombs after using one of those elevators and suddenly you can manufacture elevators elsewhere in the level. There's one spot where if you do this a couple times you actually repel down a cliff to the exit of the dungeon, behind the boss of the dungeon, and can just leave out the door. This triggers the game to continue as though you had beat the boss. Not only do you get to skip most of a dungeon you also get to skip a hard boss. He's the fire boss and skipping him means you don't need to worry about getting fire resistance, which lets you skip a bunch of other fights earlier on too. This is exactly the sort of bug you need to know about before just randomly learning the game because I'd imagine if you tried to fight the boss you'd decide you need the fire resist hat and it would alter how you play a lot of the game up to that point.
Then there's a fundamental game changing bug that feels really sketchy but is accepted practice in the community. There's a glitch in the game such that when a new buddy joins your team they don't actually come in wearing their listed equipment. They come in wearing what the last person was using instead. This bug gets fixed if you save the game and then load it back. What's really crazy about the bug is that it chains, so if you don't save/load at all you can keep using the same buddy equipment over and over. This doesn't sound do useful because your buddies get better gear as the cycle in and out... Except that if you load a game with the final buddy, soft reset, and start a new game then the equipment last used is the equipment from the end of the game and all of your buddies all game will get the stats from that gear. Stats that include resistance to status conditions and extra damage on their attacks/spells! Mystic Quest has a lot of RNG based deaths where both of your members get paralyzed or stoned or whatever... But not so much when you abuse this bug since your buddy just won't get stoned (as much or at all is not clear).
Part of me feels like loading a different save game in order to carry over the loot from that game is cheating. How is that different than using a game genie to alter my stats? But this sort of thing is standard in the speed running community. It's a glitch native to the game code itself, not introduced by an outside source like a game genie. That you need a saved game doesn't seem to change anything. People who run Final Fantasy VI do the same thing with a saved game on the Veldt where they reload over and over again to get the encounter random number counter into the right spot to get Gau faster/safer. The time spent manipulating the game in this way doesn't even count against the speed running time. This feels wrong to me, but it's the way of the world, so there's no sense fighting it. And really, it is pretty neat that you can glitch in gear from a different saved game! Creative use of game mechanics instead of just flat out cheating.
There's one final glitch I found that hasn't been mentioned in any of the videos I've watched. It was some guy posting on a forum that showed up on page 7 of the Google search results and that I haven't seen anywhere else. Apparently there's a way to get infinite copies of a consumable item once you have access to a store that sells them. The current world record for the game visits the shop to buy seeds twice; if the glitch actually works then that should shave off a little bit of time by saving a trip to the store. It would also potentially speed up some of the fights between the two shopping trips since seed conservation was a real thing he was worried about until he could go buy the second batch. If you could have infinite seeds then you could just refill your mana as desired. This could be a way to save a bit of time, but only if this random post works out.