This section is for all the stuff which doesn't belong in the other sections, so if you've got any questions which answer you can't find in the other sections, most probably you'll find it here. It will be filled randomly with anything I feel is useful, so it may be a bit disorganised cos I'll just include stuff when I think of it : ) I'll try to organise it somewhat by having a few sections, like how to earn Gil quickly, how to 'level up' quickly, how to obtain certain rare and hard-to-get items, stuff like that. If you can't find what you need here just send me an email at email@example.com and I'll try my best to help you soon as I can.
How to defeat Nemesis
Completing the Sphere Grid quickly
Super armour for your characters
Getting the Auto-Haste ability
Getting the Auto-Protect ability
Getting the Break HP Limit ability
Valefor's 2nd Overdrive
Right off we'll get to work on how to defeat this guy. He's without a doubt the most powerful monster in the entire game by far. Shinryu to Nemesis is like what an Iron Giant is to Omega Weapon, something like that.
First and foremost, try to get all your characters to complete the Sphere Grid. You can just let the 3 characters which are going to fight him do so, actually, but my advice is to do it for all of them. This is because it'll make the battle a lot easier if you can switch in a character anytime you want without having to worry that he/she is too weak or too slow. And it is a must to complete the Grid, otherwise your Strength and Agility will be too low (the rest are not too important, you'll see why).
As for weapons, make sure everyone has got their legendary weapons. For their armour actually all that is really necessary (if you use the strategy I describe later) is Auto-Haste; if you want to feel safer then you may like to go for more abilities for your armour such as those mentioned below.
By the way, when you're looking for any monsters to bribe or steal from, don't go looking in the Omega Ruins or the Sanubia Desert or anywhere else, just use the facilities at the monster arena to fight them instead. It'll save you a lot of time, and it really doesn't cost too much. You only need to go elsewhere to look for monsters which can't be captured, such as the Mimics in the Omega Ruins.
Right, so now you're ready for the battle (as ready as you'll ever be, anyway). You've got Auto-Haste (and maybe Auto-Protect and Break HP Limit) for everyone, as well as their legendary weapons, and everyone's completed the Sphere Grid. It's time to get down to advice for the battle itself.
At the start of the battle, cast Auto-Life on everybody who's fighting him, that is, whenever you switch in somebody, cast Auto-Life on him/her. This is necessary because Nemesis has 3 different attacks which can cause 99,999 damage to all 3 characters. You don't want to be wiped out, do you?
Now, if your characters have completed the Sphere Grid, their Strength should be around 200 or so, and their Agility should also be in that range. What you need to do for this battle is very simple. Just let everyone attack using Quick Hit, and you'll be fine. Nemesis has got about 10,000,000 hp, and each of your attacks will cause 99,999 damage, so it'll take perhaps 100 hits or so to finish him off. Whenever Nemesis KOs anyone, he/she should come round automatically. Have someone cast Auto-Life again on that person immediately. The important thing is to make sure that, at any time, all your characters who are fighting mush have Auto-Life cast on him/her. If Nemesis uses an attack which causes 99,999 damage to all characters, just have everyone cast Auto-Life on themselves again. Then continue using Quick Hit to attack.
It would be best to have Yuna in your party, because just before it is Nemesis's turn, if you summon an aeon, and let it fight until Nemesis knocks it out, when your characters come back you'll find that Nemesis's turn has just passed and it is your turn again. Use this tactic whenever you're hard pressed by Nemesis (for example, if he casts Doomsday/Ragnarok/End-of-the-World/whatever a few turns in a row and all you're able to do is keep casting Auto-Life over and over again to keep your characters alive).
Don't ever be tempted to use any Overdrives to attack Nemesis cos he'll counter with Ultima, which causes very major damage to all 3 characters, and very likely will KO all of them (in fact, I'm quite sure it would). Even if you have Auto-Life on everyone, when you revive it's still his turn cos Ultima was only a counterattack and if he then cast Doomsday or whatever then your party will be wiped out. Lulu's Fury will also cause him to counter with Ultima, so don't use that either. Stealing from him as well as most other skill or special abilities will cause him to counter as well, so just use nothing but Quick Hit to attack. When you finally beat him, you'll receive the Mark of Conquest.
To earn AP quickly so you can complete the Sphere Grid, you'll need a few things. Firstly, try to get a weapon with at least 3 empty slots for the character you want to level up quickly. It isn't absolutely necessary, but it'll make getting AP much faster. The abilities to put in the weapon are: Overdrive -> AP, Triple Overdrive and Triple AP. The only necessary ability is Overdrive -> AP, but with Triple Overdrive and Triple AP it'll be 9 times faster. If you have these 3 abilities, you'll only need about 70 rounds to get a character to Sphere Level 99. Sometimes when you defeat certain monsters at the monster arena (the original monsters) you may receive a weapon with one or more of the above stated abilities, if that's the case, you'll only need to add whatever ability is missing to that weapon.
To get the Overdrive -> AP ability, you need 10 Doors to Tomorrow for each weapon. You can steal these from Ultima Weapon or bribe the Mech Leader on Mt. Gagazet for them (74,000 Gil for 2), but personally I prefer just getting them from the monster arena owner. You can get 99 of them for unlocking the special battle against Catastrophe, which is all you should need since each character will only require 10.
For Triple Overdrive, you'll need 30 Winning Formulae per weapon. You can get 99 of them for unlocking the special battle against Neslug, which will be enough for 3 characters. If you want more, you'll either have to defeat Ultima Buster (slow, cos you only get 2 each time even if you do an overkill) or bribe the Sand Worm in the Sanubia Desert (quite expensive at 900,000 Gil for just 15). I'll suggest you go for Double Overdrive for your other characters instead, which requires 30 Underdog's Secret per weapon, and you can get 99 of them for collecting all 26 volumes of the Al Bhed language primers.
Lastly for Triple AP you'll need 50 Wings to Discovery for each weapon (refer to the section below on Break HP Limit regarding how to get Wings). This is really not practical (you'll need all the Wings you can get for the Break HP Limit ability!), so I only gave my characters this ability for their weapons when I get a weapon for defeating something at the monster arena which already have Triple AP. For the rest, just give them Double AP which requires 20 Megalixirs.
Note that Triple Overdrive and Triple AP are not necessary for this; they make levelling up much faster, but as I've mentioned, all you really need is Overdrive -> AP ability.
The second thing you need to do is let your characters obtain the Loner Overdrive mode. This is quite easy, really. Simply enter battle with any Flan (kill off all the other enemies), have 2 of your characters escape (leaving the one who's learning the Loner mode), then cast Slow on the Flan and Haste and Reflect on the remaining character. Since Flans only use elemental magic they won't be able to hurt you (unless you're battling a Dark Flan, in which case I can't help you), so just keep defending until you learn the Loner Overdrive mode. Some characters will learn it faster than others; for example, Auron only needs to be alone in a battle for 35 turns, while Yuna needs 180 turns. So just be patient and keep defending until your character learns it.
When you've done this, have the character who's levelling up equip the weapon with the Overdrive -> AP ability and set his/her Overdrive mode to Loner. Again, just look for a Flan to fight and have the other 2 characters escape, then cast Slow and Haste and Reflect respectively, and keep defending. Depending on what abilities your weapon has, you'll gain AP at different rates. If you have all 3 abilities stated above, like I mentioned, you'll only need to defend about 70 times to get to Sphere Level 99. If you have Double AP instead of Triple AP, for example, you'll need about 105 rounds. If you only have the Overdrive -> AP ability, you'll need more than 600 rounds. So you see why I said having Triple AP and/or Triple Overdrive will make things much faster : )
To get enough Gil (whether to bribe Malboros or Macheas or for whatever other purpose you may have), go hunting Mimics in the Omega ruins, they give 50,000 Gil each. Have Rikku equip her Godhand and you'll get 100,000 Gil for each battle (actually a bit more, cos they always appear with a Zaurus). Mimics appear in the shape of a treasure chest. Make sure you use Steal (NOT MUG!) on it before you kill the Zaurus, or that'll be 100,000 Gil down the drain. If you get a Mega-Potion or Turbo Ether, then you're out of luck; it's just an ordinary treasure chest (sure, those are good items, but what are they worth compared to a cool 100,000 Gil?). If, however, there's nothing to steal, then you've hit the jackpot! A Mimic will pop out, just finish it off and you'll get the Gil. Just be sure to let Rikku (or whoever has the weapon with Gillionaire equipped) do some action during the battle, or you won't get to double the Gil.
There are some really useful abilities you can add to your characters' armour to create your own custom armour. Firstly you'll need to go to the Macalania Woods and buy armour with 4 empty slots for every character which doesn't already have such armour (when you're fighting certain monsters, especially those at the monster trainer, you may have obtained some armour with 4 empty slots already, if you're lucky). You can buy them from the boy standing near the southern entrance to the Woods (the place where you entered the Woods for the first time after leaving the Thunder Plains). Note that you need to enter Sin first, then come out again before he'll appear in the Woods. Some supremely useful abilities are Auto-Protect, Auto-Haste, Break HP Limit and Master Thief. Some other abilities which may be good to have as well (in my opinion) are Auto-Shell (just remember that Shell works against you when you're using Cure/Cura/Curaga to restore the HP of your characters, which is why I didn't go for this ability), Auto-Regen and HP+30% (it's useful when your characters have 23,000 HP or so, then you can bring it to near 30,000).
To get Auto-Haste, you'll need to get 80 Chocobo Wings for each piece of armour. You can get 99 Chocobo Wings from the monster arena owner when you unlock the special battle against Cactuar King there, but other than that you'll have to either bribe Macheas in the Omega Ruins for them (you'll get 60 Chocobo Wings for 360,000 Gil) or steal them from either Cactuar or Cactuar King. I suggest stealing from the latter unless you have someone with the Master Thief ability, and even then you'll only get 1 at a time, whereas you can steal 2 at a time from Cactuar King without the Master Thief ability (in fact, you must not have that ability equipped or you'll be stealing Designer Wallets instead). Since you need 80 Wings, what I'd advice is to bribe a Machea for 60 of them, then go and steal until you have 80. Or if you've enough Gil and want to do this quickly you can bribe 2 Macheas (you'll waste 21 Wings), use 80 Wings to give an armour Auto-Haste, then bribe another Machea. You'll now have 79 Wings, so you'll just need to steal 1 more. That'll give you Auto-Haste for 2 pieces of armour.
Auto-Protect is not too difficult to get: you just need to get 70 Light Curtains for each piece of armour. You can get 99 Light Curtains from the monster arena ownerr when you unlock the special battle against Juggernaut. As for the rest, just steal them from a variety of monsters, such as the Iron Giant and the Geminis etc.
Break HP Limit is much harder to obtain, you'll need 30 Wings to Discovery for each piece of armour. These are among the most difficult (expensive, anyway) items to get. You only get 30 from the chocobo race at the Remiem Temple, which lets you give just one piece of armour the Break HP Limit ability. There are only 2 ways to get the rest: bribe Malboros and get 4 of them for 540,000 Gil (ouch! you'll need more than 4 million Gil per piece of armour that way), or defeat Shinryu. Actually, there is a third way: bribe Great Malboro and get 8 Wings for 1,280,000 Gil. If you're really so rich and sick of having Gil that you're using Spare Change to kill all your enemies, then this is the way to go ^_^'
The much cheaper way to get Wings to Discovery is by defeating Shinryu. That's how I got most of mine, cos 540,000 Gil for 4 Wings is much too expensive, in my opinion; I think the Gil is better spent on bribeing Macheas for Chocobo Wings. Anyway, if you defeat Shinryu, you have a 7/8 chance to get a Wing to Discovery (2 if you overkill him), and a 1/8 chance to get a Dark Matter (Dark Matter is considered to be rarer, you see, so you only have a 1/8 chance, but personally I think Wings to Discovery are more useful). So anyway, you can easily get 2 Wings for just 15,000 Gil! Shinryu only has 2,000,000 HP, so you'll be able to kill him by using Wakka's Attack Reels twice, just have Tidus or Rikku use Entrust to transfer their Overdrive gauges to him. Or you can take him out with 21 ordinary attacks. He only counter-attacks physically when you attack him, and his attacks cause no more than 2 - 3 thousand damage when you have Auto-Protect. On a sidenote, if you find that you can't easily defeat Shinryu by doing what I've stated above, don't even begin to dream of taking on Nemesis.
Return to Besaid Village when you're able to (most probably after you get the airship), speak to the girl with a dog standing next to the temple, and you'll obtain Valefor's 2nd Overdrive, Energy Blast. If she isn't beside the temple she should be in the item shop. Energy blast is much more powerful than Energy Ray, but also has a higher recovery time. Note that you can't get this immediately after Yuna joins you (as I originally thought), cos the girl who found it will be at the docks waiting to see Yuna off, so you'll have to return sometime later.
Turned out that actually it is possible to get Energy Blast immediately after Yuna joins you. Thanks to Damo Jr for pointing this out! Here's what he wrote:
"After getting Yuna in the party, talk to the girl in the house on the left hand side of the village that doubles as the town shop. She mentions that her dog has dug something up recently. Go to the house on the right where they are making fabric and 'talk' to the dog there and it will drop the soggy item that gives Valefor Energy Blast."
Actually, another gamer (Theo Shlien) also wrote to tell me about this a few days after I received Damo Jr's email, so I thought it's only fair to credit him as well ^^ Here's what he wrote:
"After they stick you on the path to the ship, I went back to the village. In the weaver's house the dog is sitting there. If you 'examine' him, he drops the slobbery thing, and you get the second Overdrive (for Valefor) right away."
Thanks to Damo and Theo! By the way, this has been verified in FFX International, but I believe it should be correct for the other versions of the game as well.