How do you turn Shaymin into its Sky form?

Question

In Black, how do I change my Shaymin into its sky form?

Answer 1

You need a gracidia flower to change shaymin.

There should be a lady in the Pokemon center in Lacunosa Town who talks about the Gracienda flower. I'm sure that if you have Shaymin with you, she will give you the Gracienda flower. You might have to do this during the time that the Gracienda works, and Shaymin might have to be first in the party.

-Kyogreruler

PS it needs to be the event shaymin with the fateful enounter in it's summary

Answer 2

Give your Shaymin a Gracidea , which will change Shaymin's form into Sky Form only when its not night of frozen. You can get the Gracidea from the lady inside the Pokemon Center in Lacunosa Town when Shaymin is in the front of your party.
*Your Shaymin must be legitimate, not a hacked one or else this will not work. It must be from an Event or Caught in Platinum in Flower Paradise with Oak's Letter.