From what I can recall the first mission that gave me a bit of trouble was the werewolf one.
As far as the Signs are concerned, I've mainly used the mindfuck one, the trap one and the fire one. Shortly before I stopped playing, I finally cottoned onto the fact that the telekinesis one is handy against large groups of mooks.
I barely ever used the shield sign—only when the boss monster really required it—I just dodged like a mad fucker all the time. I'd been doing quests at around the listed levels before I got bored.
