You can find out in the toolset, but that's not very helpful, I know.
The required Lore skill is usually within 3-4 of the required level to use/equip the item and is typically equal to or less than the required level.
Incidentally, I know it's kind of ambiguous, but...
LORE -- Acronym meaning Layonara Online Reference Encyclopedia; Web site with all sorts of reference information about Layonara.
Lore -- Name of a skill in D&D/NWN
lore -- usually used as "world lore"; refers to the stories, history and cannon of Layonara.
Yeah, I know...splitting hairs, but lots of people mix them up and believe it or not, I spent a few seconds wondering where minimum Lore was listed on LORE for items...heh
Anyway, hope that helps.