well in Pokemon diamond for the Nintendo ds he goes to...well you know the beach just outside the town? no? OK then! so you are in the town and you know the building just left of the swamp challenge thing? well go in there and go out the other side and you'll see a Field go into the Field (you might be attacked by a wild Pokemon but i just fled) well cross the Field and you'll see sand go into the sand and to the house at the beach you see him yet? no well then go to lake valor he must be there!
you find it in the galactic HQ
try battling them..
You may not join Team Galactic in Pokemon Pearl or Diamond.
No
Both Pokemon Diamond and Pearl have Team Galactic as the main antagonist team.
You will need Galactic key and this how to get Galactic key you will need to talk to a Galactic team mate by the Galactic HQ.
With the Galactic key you can unlock any locked doors in the headquarters.
go in yellow circles and stairs
It depends on who your battling.
You can't join
it's barboach. You can get it by battling or fishing it with a super rod.
All you have to do is Batlle him and get the Galactic key card