Create Situations not Plots
In preparing for the game I've planned out a chunk of a world where the dwarfs can roam. There are some hooks here and there but no "main plot" planned out. Most hooks come in the form of places to explore and looming threats rather than an innkeeper asking you to find his hat some goblins stole. I like the tip I heard somewhere, "plot hooks not plot hammers".
A hook can be ignored or saved for later, a hammer is going to be much more focused on pushing you in a particular direction. I'm hoping the map I've provided is already suggesting a hook or two before we've even started.
I Cannot Control the World Fully
Sure to be a contentious point. I've poured my heart into creating the world and have tried to design it in a way that will give the players a great experience, but once they step into it I'm not going to have complete control of it. It's all laid out, populated with threats and scattered with hooks and treasures. Many of these will appear when the dice decide, rather than I. If the players wander into the Underworld and are finding it too hard or too easy I have no intention of tweaking it on the fly. I also know there are some random encounters noted down that will be dangerous stuff.
By no means will I try and kill the characters but I won't tone them down the hazards when things get tough. I'm hoping I've planned such places in a way that they'll be sufficiently aware of the threat, though. One thing that always bugged me about Oblivion was that monsters would scale their power level to however powerful the player character was at that point. I'm standing on the other extreme of the scale with this game.
A Good Map will provide Hooks
I always love a game with a great map. I want to see interesting looking locations and see some intriguing places named. I remember when I first played Link to the Past I opened up the map and decided I wanted to go and explore the Swamp Ruins. They weren't relevant to the main plot until later in the game but I still headed there and took a look around because what's not to like? Swamps are cool and Ruins are cool.
I'm hoping the map for the starting area of my campaign will do the same.
A larger version can be enjoyed here. Good old Hexmapper.