While you'll be doing a lot of walking in the game, there's a lot of content in and right around the cities. But though you can find encounters on your own, it makes more sense to do things as part of a mission. Currently there seem to be a few bugs with the missions. Friday night I encountered frequent bugs with missions, ranging from waypoints leading to nothing to NPCs failing to deliver rewards. The most reliable missions seem to be the dynamic ones spawned by the mission terminals. These will frequently send you out in the world to kill a group of monsters and eliminate the lair from which they spawn. I'm still not sure why there are amphibians on a desert planet, but a job's a job, right?