Another way is to do Renown Quests. Fixed zones marked by a Heart, they are one of the most efficient ways of leveling. This works by giving you a number of tasks to do, and once you complete a sufficient number you will be awarded with EXP and Karma Points. A very simple and effective way of leveling.
Dynamic events, probably one of the most anticipated things of Guild Wars 2. These events are totally random, and come in many different forms. Upon coming across one, you get a little “alert message” which tells you where and what the event is. Events include escorting various people (who attract copious amounts of enemies), to defeating a big and ugly boss. More events include defending whole cities or towns and repairing them, turning into animals such as pigs and doing quests,and killing centaurs. You know, the norm in the world of Tyria. Naturally the more you participate, the more EXP your character will earn.
My personal favorite way to gain EXP. WvWvW throws you into combat with 2 servers not including your own. Completing events, killing other players, and gaining checkpoints all give EXP.
Guild Wars 2 easiest way to gain EXP is simply exploring. Arenanet added generous amounts of way-points, vistas, and points of interest in order to visually please the gamer, while giving him EXP. Small square points on the map are points of interest, waypoints are represented as diamonds, and vistas as red arrows. Exploration also works in conjunction with dynamic events. The more areas you explore, them more dynamic events you will come across.
Daily achievements offer another easy way of gaining EXP. These achievements are aachieved simply by killing varieties of creatures, killing a number of creatures, gathering materials ect. They are refreshed everyday, and provide a great way to rack up that EXP fast.