There are various ways to level up your character, some very slow, and some optimal, to name just one way to differentiate those different ways.
You can of course find out for yourself what really works, but here is a link (curtesy of EJ) to a leveling guide for your diablo characters: Diabloii.net Leveling Guide

One thing this form does not show is concentration of monsters. There are some areas that might have slightly less xp per monsters, but the monsters are denser. Hence more xp per minute. This kind of fine tuning you can do through experience. In general this table will keep you from wasting time in leveling a level 60 sorc in Act 1 normal.