These are just tips, you don't have to follow any of these.
1) Skip party dungeons, they often take too much time and if you want to level fast I'd suggest just going to the next area.
2) Grab the book quests in every area, you can complete them alongside the main quests for extra exp
3) Use F1 to quick target yourself
That's all I got right now, if anyone wants to contribute I can add them to the main post