This document provides a guide to leveling up quickly in Diablo 3. It explains that repeating quests is an effective strategy for gaining experience points. In normal mode, completing tutorial and other early quests can get a character to level 30. In nightmare mode, better equipment is needed to handle tougher enemies, and the Lieutenant Vachem quest provides good experience. In hell mode, the strongest gear and skills are necessary, and repeatable quests allow continuous experience gain.