by being awesome
You have to go through the Ice Path first.
you get get it in Ice Path before Blackhorn City and after Mahogany Town.
blackhorn city i think its next to mahogany town
you have to get the team rocket dudes out of the radio tower
Aliza town
Blackthorne city is not in Pokemon Diamond but in Pokemon Heart Gold/Soul Silver
it should be in olivine city
In fuchsia city.
blackthorn city
dodo
The Pokemon Daycare is on the route South of Goldenrod City.
The Pokemon Fan Club is in Vermillion City.