Meeting Special Pokemon
Articuno, Moltres, Zapdos - Appears after you talk to Professor Oak in Eterna City.
Drifloon - Found every Friday at the Valley Windworks
Spiritomb - Get the Odd Keystone and use it on Route 209 at Broken Stone Tower
Rotom - Examine T.V in Old Chateau from 8 PM - 4 AM
Uxie - After you battle Giratina and then go to Acuity Cavern
Mesprit - After you Battle Giratine and starts to wander over Sinnoh.
Azelf - After battle Giratina and then go to Valor Cavern
Dialga, Palkia - After talking with a Elder in Celestic Town head to Spear Pillar
Heatran - Talk to Buck at Survival Area and head to Stark Mountain
Reigigas - Have Regice, Regirock, Registeel in your party and head into Snowpoint Temple.