go to te mansoin and find a safe

you can get him before you beat Sephiroth

the code for the safe is right 36, left 10, right 59, right 97. the4n you'll fight a monaher use magic untill he chances, then no magic just attack

Get vincent by going in the Shin-Ra mansion in Nibelheim, go up the stairs and left, and into the room with a safe, the code to the safe is right 36, left 10, right 59, right 97, make sure you do not go PAST these numbers (eg. when you're going to 97 you go to 98 and back down to 97, this will not work, has to be perfect).
You may not get it right the first, or second, or third time but just keep trying as you get Vincent, and the handy Odin materia

Get vincent by going in the Shin-Ra mansion in Nibelheim, go up the stairs and left, and into the room with a safe, the code to the safe is right 36, left 10, right 59, right 97, make sure you do not go PAST these numbers (eg. when you're going to 97 you go to 98 and back down to 97, this will not work, has to be perfect).
You may not get it right the first, or second, or third time but just keep trying as you get Vincent, and the handy Odin materia