go to the Pokemon league
go to the Pokemon league and defeat them
You can't really go further then that. The pokemon league contains the toughest trainers in pokemon platinum.
You automatically go to twinleaf town.
go to the Pokemon league north of sunyshore
go to serebii.net
all you half to to is go there whenever at night.
Beat the Pokemon league again and go back to spear pillar and you will see dialga again.
get him on Pokemon ruby,Sapphire or emerald on gba and migrate him into platinum catch him in a gba Pokemon game and then go to pal park after the Pokemon league and migrate him to platnium
First, go to the Pokemon Leauge.Then, right above the Pokemon League is route 224
you go to the path to the Pokemon league and there's a double battle a boy and a girl you go to the and they have a ocilery
You get to the Pokemon league and you start from the end of victory road and there you go to a cave you see.