Use a text editor such as notepad to edit the "quests.xml" file in the game directory. Increase the value of the XP lines, but keep it within reason to avoid losing bonuses that happen with level ups. Values of 500 to 1000 XP for each quest should work well until you get further into the game and are at higher levels. Also, note that each quest has a Quest # that give clues as to what quest it effects.