Instructions
Thief Abilities
Level your thief's Detect Traps ability to at least 100 before you start "Watcher's Keep" or "Throne of Bhaal."
Turn on your thief's Detect Trap ability. If your thief is under 100 in trap-detection skill, walk slowly and carefully in areas likely to be trapped so that you don't trigger the traps before they turn red.
Use your thief's ability on a trap to disarm it. If your thief skills are too low to disarm a trap, use a thief's Potion or a Potion of Perception to increase your skill.
Consider dual-classing Sarevok to thief in Throne of Bhaal if your player character is not a thief. Note that Yoshimo cannot be resurrected and either Nalia and Imoen both dual-classed too early will have extremely weak Thief Skills.
No Thief in Party
Use a cleric to detect traps by casting the Detect Traps spells.
Summon a low-level monster or undead and have it trigger any trap on the ground you cannot avoid.
Move your party well back from a trapped item or chest. Have one party member fully buffed with protective spells trigger the trap. Use the Wizard Spell to Knock open the item.