Once you reach the Temple of Hatshepsut on Act 2 after beating the Telkine, go in side and activate the Respawn Fountain.
After this turn around and exit the temple and defeat the 6 Dark Obelisks. Thes eprovide an insane amount of XP. Sometimes Hero Monsters will also spawn allowing for more XP and rare drops.
Oncew done save the game, Quit to menu then continue.
Rinse and repeat.
The XP Grinding in this game is actually insane and extremely steep. So much so that finishing the game twice will net you like level 40 MAYBE.
This is your best bet early in the game on normal.