Level 60: Complete Rite of Passage (hell difficulty).Level 41-60: Repeatedly clear the Chaos Sanctuary and Baal (nightmare difficulty).Level 40: Complete Rite of Passage (nightmare difficulty).Level 25 - 40: Repeatedly clear the Chaos Sanctuary and Baal.Level 15 - 24: Clear Tal Rasha's Tombs in the Canyon of the Magi.Level 1 - 15: Repeatedly clear Tristram.Hunt for Experience Shrines in different Acts (act 1 usually is the easiest) as you get 50% more experience while it is active, but be careful not to get too close to any monster that can curse you such as unique monsters with the 'Cursed' status, Oblivion Knights, or Baal himself as curses override any active shrine bonus.This is particularly important for Hardcore players as well, for obvious reasons. Don't put yourself at risk of death in Nightmare and Hell since the penalty on death is 5% and 10% respectively.Some areas will require the completion of quests to advance. Gain access to areas by having higher level characters share waypoints.Melee players may get their weapons (and mercenary's weapons) Enchanted by a Sorceress to provide a dps boost.Asking a higher level character to help clear areas may be better if their speed makes up for the level penalty.

Players should always try to accomplish these steps in full games since the amount of experience increases per player in the game.

Diablo 2 power leveling guide