to get vincent you have to open a safe in nibelheim mansion.afterwards you get a key which opens a door near the library where you see sephiroth open the tomb in the door then talk to vincent as much as possible then when you go he will chase you.can someone post in how to find out the safe combo or the combo because i forgot.

to get yuffie. fight in the forests anyhere and you should get into a fight. when you win answer all of her question to beasically say i dont wanna fight again then pick one of the last options as "lets hurry on" if you fail the first time you can try again.