Article: For MMO vets, yes, level grinding is still the main way to get XP. For MMO newbies, level grinding will be the bane of your existence. Start by getting out into the world. Specifically, get out into the wilderness. The more dangerous the environment, the better. Step 2, as it turns out, is to kill a bunch of stuff. Use your preferred method and try to kill things on your own to maximize XP gained. Have fun! (just kidding) The infamous "Step 3: Profit". Just keep killing things and getting the XP. It may be boring sometimes, but eventually it adds up and you'll get to where you want to be.

What is a summary?
Explore the world. Kill creatures. Rinse and repeat.