Best tactic I've seen is to make full use of that first room you arrive in. Pick off the opponents one or two at a time by luring them back to that room. Placing traps right in the doorway works wonders, especially when the lich appears there.
Also, after each "gap" in the action, do a quick save. This will stop you from having to do the whole fight over if you mess up later in the fight.
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Death is only the beginning...