To act like the character Yuffie Kisaragi you must be very
cunning, sneaky and eager to get your hands on one thing, materia.
You're also very ignorant and selfish and only focus on materia as
your objective. (This is why she steals from Cloud's party, to get
materia from them) But you're not completely bad, you have a hyper,
fun and funny side to you as well as a clumsy one at that. So the
best advice on being Yuffie is to just, be cheery, annoying and
sometimes a pain in the neck! Though, she is more likely to be on
the cheery and hyper side than the other. :)