Intro: Final Fantasy X was the first Final Fantasy to the PS2. It's a story about the famous blitzball player, Tidus, who is taken 1000 years into the future by a creature called Sin. There, he meets many people including the summoner Yuna, who is out to do Sin in. The story follows their travels from Yuna's homeland of Besaid to what was once Tidus's homeland, the ruins of Zanarkand. Final Fantasy X is also the game with the coolest video game character in history, the samauri, Auron.
Familiar Faces: For those of us that have played both FFX and FFX-2, we are able to recognize familiar faces from the first game in the second game. But what about the other way around. Here are some characters from Final Fantasy X-2 who are hidden in FFX. (Note: I know that these are the locations after you obtain the airship and get everyone to sing the Hymn of the Fayth. If you aren't that far in the game, these characters might not be in these spots.)
Valefor's Secret Overdrive: Alright, so it's not that secret, but it is handy and easy to get, and you get get it before you even have the chance to battle with Valefor. After you arrive in Besaid and have rescued Yuna from the Chamber of the Fayth, talk to the girl working at the shop (the southern-most hut in the village on the left). Look at what she has to sell (buy some supplies if you need to), then leave. Before she let's you go, she'll tell you that her dog found something weird the other day. Go find her dog in the northern-most hut on the right side of the village. Walk up to it and press X. It will say you have obtained Valefor's Overdrive, Energy Blast.
Double Aeon Overdrive: This is a simple trick, but useful against tough bosses. First, get one of Yuna's aeon's overdrive gauges full, and don't use it. Then get Yuna's overdrive gauge full, and, once again, save it up. When you come across that tough boss that you just can't beat, use Yuna's overdrive. It will summon one of her aeons with their overdrive bar full. Use the aeons overdrive and you'll see that the bar is still full. If you use the aeons overdrive a second time, it will empty out. But aeons overdrive bars can go up really fast, so it's best if you use your two overdrives right away.
Lost in History: In FFX-2, you will no longer see aeons, the fayth, or summoners (plenty of ex-summoners, but no actual summoners). There are a few other things that you won't see, so enjoy them while you can:
Fun with Zombie: Look up above and you'll see that Zombie Stats won't happen in Final Fantasy X-2, which can be a good thing or a bad thing. It's good, because that means enemies can't inflict it on you. It's bad because you can use it against enemies. But for now, you can use it, so let's have some fun with zombie stats.
Mad'c cbayg Al Bhed: This is cool. This site, Final Fantasy Insider, has an Al Bhed translator. You can translate English into Al Bhed, or the other way around. Bnaddo cfaad, ech'd ed?
Here's a cool little trick: Dark Flans are extremely tough to kill. Have a character with Zombietouch or Zombiestrike on their weapon in the battle. Attack it until it's zombiefied, then have another character use a phoenix down on the flan. Since healing items harm zombiefied creatures and character, guess what happens to the flan...
For those of us who think the airship battle with Evrae was tough, we'll see just how tough he is when he shows up later. Later in the game, after Bevelle has imprisoned you, you'll meet up with Rikku and Wakka in a large pool. You'll also meet up with Zombie Evrae. He's a super easy kill, since he starts the battle with Zombie Stats. Just keep using phoenix downs. They won't kill him, but they will inflict more damage than your characters can.