Use the walkthrough on this site, it's very good.
Spoiler
Keep in mind that Kuo Toa should be dealt with first, because the bolts can stun mind flayers. Also wand of cloudkill is good for mass destruction (doors are essential for this strategy).
Shield of Baldurian and Cloak of Mirroring is essential for a safe passage in the Beholder dungeon. Elder orb can cast imprisonment, but then they can't imprison what they can't see, can they?
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Make sure you save some KT bolts for the guy-vampires in Bodhi's lair. It makes short work of chapter five and six IMO.