To find Yuffie you must walk or drive through any forest area until u encounter Yuffie. When fighting here she will not be called Yuffie she will be called "Mystery Ninja. She shouldn't be too tough to beat and once you do you will be taken to a small map where Yuffie is lying down. Once she gets up you will be taken through a long dialog. To get Yuffie in your party just follow these instructions. Do not use the save point. You must respond with the correct answers through the dialog or you will lose Yuffie and have to repeat the process of getting her again. Here is how the dialog should go if you want to get Yuffie.

Yuffie-"You spike headed jerk! One more time let's go one more time!"
Your Answer-"Not Interested."
Yuffie-"Your pretty scared of me, huh!?"
Your Answer-"……petrified."
Yuffie-"I'm really gonna leave! REALLY!"
Your Answer- "Wait a second!"
Yuffie-"You want me to go with you.?"
Your Answer-"……That's right."
Yuffie-"All right! I'll go with you!"
Your Answer-"……Let's hurry on."

After this conversation the name screen will come up and Yuffie will join your party.

-Finding Vincent

Vincent is locked in the basement to the Shinra Mansion. The door is locked but the key isn't that hard to get. To get the key unlock the safe on the top floor of the mansion and fight the boss, Lost Number. The code to unlock the safe is Right 36, Left 10, Right 59, Right 97. Don't go over any of the numbers other wise u will have to start over. After winning the battle you'll find the basement key in the safe. Go unlock the door to find Vincent resting in the middle coffin. Tell him about Sephiroth and he will go back to sleep. Wake him again and he will tell you his name. After this leave the mansion. On your way out he will stop you and join your party.

Once you have been locked out of Midgar there is still a way to get in with out using a parachute. Go into Midgar and right outside the gate there is a man talking about a lost key. Well now it's off to bone village. When you get there tell the foreman you are looking for "normal treasure". Place all of your hired hands around the top area of bone village. They will find a "key to Sector 5". Now you can come and go through Midgar as you please.

Lucrecia's Cave

After getting the submarine or a gold chocobo you can reach Lucrecia's Cave. This gave is located behind a waterfall in a lagoon in the Nibel are. To get here by sub you must come through an underwater cave just east of the lagoon and park against the rocky ledge left of the waterfall. The gold chocobo can ride over the mountains and dismount near the ledge. Visit the cave during disk 2 with Vincent in your party to learn a lot more about Vincent's life. Visit the cave during disk 3 and you will get Vincent's final limit break and last weapon.

Costa Del Sol's tropical getaway

In Costa Del Sol there is a real estate agent that is selling off President Shinra's vacation home for a low low price of only 300,000 Gil. There's not much you can do here besides rest. There are some items in the basement but you can get them without forking over the Gil.

Lucky 7

Any character in your party that is reduced to the HP of 7777 after and attack will go into the lucky 7 attack mode. This player will go on a mad rage attacking enemies nonstop landing 7777 points of damage each time.

Special Cinema

After Cloud finds himself, visit the basement of the Shinra Mansion. When entering the library area you'll go to a special cinema. Enjoy.

Sunken Gelninka

If you visit the Sunken Gelnika as soon as you gain control of the submarine, you will be able to encounter the Turks, Reno and Rude. They are extremely powerful and boast new weapons and attacks, so be wary. Level 50+ is advised, both because of the Turks and the deadly beasts inside.

Unlimited Sources

You can get unlimited sources even after leveling to to level 99 to boost your stats by Morphing the following creatures:
Bad Rap - Luck Source
Poodler - Speed Source
Serpent - Mind Source
Unknown - Power Source
Unknown 2 - Guard Source
Unknown 3 - Magic Source
The locations of these monsters can be found in the Final Fantasy VII Walkthrough section.

Secret Room In Cosmo Canyon

In the Item Shop in Cosmo Canyon, when you first visit it there is a little doorway that is cut off by a red bar. If you come back later in the game, say a disc later, the door is now open and you can go through it to a secret back room where you can collect Full Cure materia, Elixir, and Magic Source.

Extra Gil and Exp

If you want more Gil and Experience from your battles, the only way is to equip the Gil Up and Experience Up materias on characters in your party. You can acquire these materia from chocobo racing.

Free Prizes

If you have a Chocobo that is in Class S, you might want to take advantage of some free prizes. If you win fifteen consecutive games in S Class racing with your chocobo, you can get a number of free prizes from Estel, they are listed as follows:
Cat's Bell
X-Potion
Sneak Attack
Megaelixir
Bolt Plume
Fire Veil
Sprint Shoes
Counter Materia
Magic Counter Materia
This only works once, take note of that.

Turtle's Paradise Flyers

Turtle's Paradise in Wutai is holding a contest they have placed 6 flyers all over the world. If you find them you get a special prize. Here are the locations of the flyers.

Flyer 1- In Sector 5. Look inside the house on the east side of town. You'll find the flyer tacked on the wall in a boy's upstairs room.
Flyer 2- In Shinra HQ. The flyer is stuck to the bulletin board at the back of the lobby's first level.
Flyer 3- In the Ghost Hotel at Gold Saucer. It's inside the hotel's lobby next to the shop's entrance.
Flyer 4- In the Tiger Lily Arms shop in Cosmo Canyon.
Flyer 5- In the inn at Cosmo Canyon.
Flyer 6- In Yuffie's basement in Wutai

Once you have found all the flyers go to Turtle's Paradise in Wutai to collect your prize.