How do you level up fast on endless online?

A good way is to make a friend who is really high level. Ask them if you can join their party and let them train you on some really high lvl monsters. While they're doing all the work, sit back somewhere safe and watch. Every monster they kill, the EXP will divide between the two of you. Another good way is to go to the Moles, I really can't be bothered explaining where they are so just ask someone near by to take you. It's not very far. Once you get there go into the building and start the quest. Every 50 Moles you kill you will get 2000 EXP. And They are very easy to kill, but there are usually alot of people there. HAPPY TRAINING!