Powerleveling to 80.
Just go through your story doing all the hearts and gathering you can on route.
jewelery and cooking are fast exp, if you have lots of mats or money you can do all the crafts and get to 80 without setting foot in another area. I would personally recommend going into the world and getting some skill points to fill out your character though
Maxing all 8 crafting profession will get you to level 80 in a few hours but this will take up a lot of gold. And as Yargesh notes some skill points would be usefull, leveling alone only gives you 80 which may be be a few short to get all the skills you want.
Besides crafting exploration is something that gives you good exp. Just run around the map ignoring mobs and hearts. Take all the waypoints and POIs this should give some good experience. While doing this stopping at a few skill points will help you in both skill points and experience.
If you run into any events do a bit there as well as they also give you experience.
I gain levels mostly by exploring. Especially in the first few levels. Anet was kind enough to put events by hearts, so that you can get the heart by doing the event, twice as much xp! As others have said also crafting. Cooking is a big one and jewelry is good since you don’t need fine crafting materials.
Just follow your story line, that will take you to the area’s you need when you need them. Want to level fast, explore, harvest nodes, kill mobs, craft, do hearts and events as you come across them. Also do you daily(s),, which if you do PVE you can do the PVE quite easily by just killing mobs, gather and do events. You can do a level easy. A full set of Orr exotic will cost 252,000 so get those dailies done.