Go to an event. You could use the action replay cheat cartridge, but i wouldn't recomend it. It mucks up your game and bans you from wifi. So go to an event, they normally occur in America or Japan.
no
You have to get Oaks letter an a special day and go to victory road then to the ocean and professor oak will be there with a rock and shaymin will appear.
Via Nintendo Wifi.
if you already have the national dex you can be able to go to his lab
no you have to get is from an action replay or go to a Pokemon event
You use it at the smooth rock. Then you can get shaymin.It is on route 224.
By action replay or events that that come rarely
to get professer oaks letter then you must first have the mystery gift from Jubilife city.You must also have the national pokedex. Save your progress.Then turn your Nintendo ds on and select mystery gift.Then you must select via wi-fi connection and choose oaks letter. then you must play Pokemon diamond and go to any poke-mart and talk to the man in green and he will give you oaks letter. ----------------------------------------------------------------------------------------------------------------- Can u do it any time, or do u have to do it by a certain time?
You have to get it from an event, but there hasn't been any event lately for Pokemon diamond/pearl. Most of the events are for platinum now, oaks letter was given out a feew weeks ago for platinum. You can keep a look out though by going to serebii.net
You can get the Item finder from Professor Oaks in Pokemon LeafGreen. Professor Oaks is found on route 11 just out side of Vermillion City.
No.
i done this for the crack of it :D