Elddim
Talk to the priestess in the cathedral to get the Elddim townstone quest. You can find it in the Ancient Crypt. Turn right once you enter the crypt area (i.e. not the rock walled tunnels) and follow the path through a couple of rooms. It should be in the first sarcophagus you open (which is a small side room adjacent to the room with the signs pointing in opposite directions), but will be locked if you haven't talked to the priestess first.

Crystwind
Talk to the woman standing beside the Crystwind smith. She'll give you the Crystwind townstone in exchange for the Rune of Diamonds. That can be found by going to the grasslands area outside of town and killing the foes (krug and skeletons) near the ruins.

Fallraen
Make sure you talk to the apprentice in the magic shop first, otherwise you might not be able to get the townstone (i.e. it may not appear unless you talk to the apprentice before reaching the area with the stone). Exit the town from the north gate and take the path up and to the right. You'll enounter two caves, the first one (a "Furok Cave") leading to the Fallraen townstone, which is near where you get ambushed by the army of Braak casters, and the second leading to Meren.

Meren
Get the quest from the priestess who mentions that the temple is to the South. Follow the signs that point to Lang until you get to a point where the trail on the ground goes in the opposite direction from the sign pointing to Lang. Follow the trail and you\'ll find a displacer and a ranger standing beside it. He'll point you to the path to the Temple of the Stars. Be ready to be ambushed by a small herd of hell boars once you enter the area or pick up the townstone.

Lang
The priestess in the magic shop/tent will give this one to you.

Quillrabe
Follow the path to Hiroth (exit from the top of town, near where the H.U.B. is). This one's a bit of a trek, but you'll eventually get to the Dragon's Nest. Kill the Dragon Queen to unlock the chests (one of which contains the Quillrabe townstone).

Hiroth
You don't have to get this one. The priest will tell you that he conveniently already placed it in the circle in Hiroth and give you the quest to place the rest once you've gotten all the other townstones.

Grescal
Go NE a very short distance from town (you can follow the torchlight stands that start near the magic shop), to the Abandoned Ruins. Go down the stairs and find the elevator down to the next level (just keep making left turns at every intersection). One of the rooms will have a "brick" (level/switch in the wall) behind a chest that you can use to open two hidden doors. The one closest to the brick contains the Grescal townstone.