The Lord of the Rings Online official site has been updated with a guide to the advanced search feature of the LotRO Lorebook.

The LOTRO Lorebook is a useful resource for players seeking information about anything in the game, from creatures and items to characters and locations! One way to fully maximize its utility is by using the Advanced Search feature, which allows you to search by category even if you don't know the exact keywords for your search Instead of entering text, you can start your search by selecting one of the categories in the Advanced Search panel, which is located beneath the Basic Search box:

Categories include Weapons, Armor, Quests, Deeds, Traits, NPCs, and Recipes. Each category permits you to select and input as much, or as little, information for a query as you like; you don't even have to enter text into the text fields in order to perform a search!

Read more here.