Final Fantasy VII - To Get Vincent Valentine in you party

LUCKY 7777:
Get ur characters hp higher then 7777, then go to a random battle, if you lucky enough, they will hit you exactly at 7777, then you will go hyper and hit all or one enemies 7777.

To get Yuffie:
Yuffie can be found:
In the forests near Gongaga.
In the forests near Junon and Fort Condor.

You'll probably have to get in a lot of fights before she shows up, but when she does, beat her and talk to her. Answer her questions like this:

AND DON'T GO TO THE SAVE POINT OR ACCESS THE MENU.

Q: One more time, let's go one more time
A: Not interested.

Q: You're pretty scared of me, huh?
A: Petrified...

Q: I'm gonna leave I mean it
A: Wait a second

Q: So you want me to go with you?
A: That's right

Q: All right I'll go with you
A: Let's hurry

Getting the Limit Manuals:
In order to use Limit Four Breaks you need to find the manuals to each character.

Cloud:
Trade 32,000 battle points at the Golden Saucer.

Tifa:
Go to Nibel area Tifa's house and play these piano notes: X, Square, Triangle, L1/R1 Triangle, L1/R1 Square, X, Square, Triangle, L1/R1 X, O, X, Square, X. Then press start and search Tifa's music sheet.

Barret:
A lady will give it to you in North Coral.

Aeris:
southeast of Midgar there is a small cave with a man living there. Talk to him when you have battled a certain number of battles that end in the same number, such as 122, 133, 144. He will then give you a Mithril orb. Take the Mithril to the Blacksmith's house on the south peninsula near Cosmo Canyon. He will trade you for he limit break manual for the Mithril, or you can choose to have a gold bracelet.

Red XIII:
In the Nibel area there is a mansion and on the second floor of this mansion there is a safe. To crack this code turn right 96, left 10, right 56, and right 7. Then the safe will open to reveal a miniboss. Kill the miniboss and ou will rcieve Red XIII's Manual.

Vincent:
Land near the waterfall and use the green, black, gold choobo or the submarine to paass the mountain. Then enter the waterfall. You must have vincent in your group and must be done first in in disc 2 go forward and it will show Vincent's past. Then leave. Return if you are already in disc three and you'll get not only the manual but a wepon of Vincent.

Cid:
Cid's manual is in one of the chests in the sunken plane.

Yuffie:
Go to Wutai and enter the tower with yuffie and let yuffie beat all the bosses including her father and you'll get a manual and Laviathan materia.

Materia:
At the top right hand side of the map is a craterlike island with a cave that can only be reached with an all terrain chocobo, inside is the best materia in the hole game, it'll make beating the game a piece of cake. PS. there are caves all over the world with special materia most can only be reached with specially bred chocobos.

Summom matria:
At the chocobo farm go to the chocobos and press X then press WRAK. The chocobos will do a dance. After the dance you will get a Summom matria.

W-ITEM:
In Disc Two near the very end you'll find yourself in the sewers of Midgar again. When you end up there, move backward so that it seems Cloud is having a close up. You will go back a screen, continue this about 7 or 8 times and you'll come to a hallway with a cage, in front of you will be the yellow W-ITEM Materia.

If you are in Disc 3 and missed this, and this has worked for me, you can go to Bone Village and dig it up in the same area as the Midgar Key.