One hurdle in checking completed quests in WoW is remembering which ones have been done. Utilize the Quest Log (default ‘L’) to view all active, unfinished quests, and browse the Completed tab to locate any finished ones. Sorting the list by zone or quest type aids in easy navigation.

An additional challenge is discerning which quests count towards achievements or questlines. Consider installing an add-on like Quest Completionist, which provides detailed information on quest status and ties them to relevant achievements. Furthermore, checking the WoWhead website for specific questlines can reveal which ones have been completed.