You need to construct a world that the characters and the players care about. This means locations that include 'touchstones'. It means NPCs that the players can love hating, as well as love rooting for and helping. It means plots that the plahyers choose to be involved in.
Choice is a powerful tool in the RBDM toolbox. The players choose to have their characters involved in the campaign elements. This doesn't mean that they have to choose every element. But it does mean you, as the DM, are looking for something special in every choice the players do make. These choices, where the players tell you (though not always directly) what they care about, will become the elements that you may, or may not, twist in unusual directions.
The RBDM always listens to the players, though the players are not always aware of what it is the RBDM is hearing.
One example:
That chance encounter with the pot merchant on the road? The players loved the fact that you gave him a little quirk in his personality. You created the encounter with the intention of not having every random encounter be a monster to fight. This random encounter is just an average joe that is trying to make his way in the world. The players decide that the PCs will camp with him and watch out for him for the night. Maybe they even buy a skillet because they need to have something to fry eggs on each morning. The silver or two it cost them meant nothing to their treasure allocation, but it helped him a little bit.
To some DM's this is a blip on the radar. Some DM's might be annoyed that the 'flavor encounter' took so much time that night instead of getting to the dungeon. Some DM's will squander this gem of an opportunity. You see, the players just told you that they found an NPC that they want to care about. They want to see the little guy succeed. This NPC, chance encounter that he started as, is a link to the campaign. Verisimilitude is what we might call it. But the RBDM sees it as something more. This is an opportunity.
Some DM's will see this opportunity and leap upon it. They will pounce and immediately put the hapless NPC in a terrible situation and the PCs are the only people that can help.
That isn't a terrible option. After all, the PCs now care about something and it is good to use this touchstone to create a new adventure hook. But the artful RBDM won't immediately do this.
Instead, the PCs will later encounter the merchant somewhere else. He will be excited to see the PCs. He may share news. Suspicious players will keep waiting for the 'gotcha'. The Merchant is possessed, or lycanthropic, or has a sob story. But is that what the RBDM will use him for? Maybe, but maybe not.
Why not have him just be a merchant that the PCs helped out once and is now happy to see them?
The RBDM will carefully harvest these chance encounters throughout a campaign. The RBDM will retain consistency - the merchant won't show up when the PCs cross the ocean, but he will be a friendly face when they return home weeks, months, or even years later. Throughout a campaign, the RBDM will have several of these NPCs that the PCs care about. Some will be powerful NPCs, some will be weak NPCs, some will be somewhere in between.
When the PCs encounter these NPCs throughout the campaign, many of them will be fine. They will be contacts, they will provide news. But sometimes the DM will use these NPCs for something else. The pot merchant might show up across the sea. But now he is a refugee because the homeland the PCs left is torn asunder in war. Or maybe the merchant is a werewolf and now the PCs need to try to cure him, or just kill him. Or maybe, just maybe, the merchant is cursed with an invisible imp on his shoulder. The silver the PCs paid him with was cursed and over the last few months he has been hounded by this imp. The curse didn't take effect until after the new moon, after the PCs had spent all that silver. Now there are innkeepers, merchants, wenches, and even a sage affected by this curse, scattered across the land. The PCs didn't know they were cursing these people, but they didn't check to see if the silver was cursed did they? Sure, they took the silver from the ghoul that was old man Miser in that town. Who knew that old man Miser's family was cursed? All of his money was buried with him and so it arose with him the day he started feasting on the flesh of those poor town people. The PCs saved the town by killing the ghoul and taking all of his money. But then they cursed the land for leagues around when they started spending that silver. Poor average joe, the pot merchant, was just trying to make a living when the PCs bought that skillet. He didn't know the great heroes would curse him...
But it only works and makes you a RBDM because the players care about the pot merchant, and they care about the campaign world. And they know that if they had checked for magic, or curses, or anything, they could have avoided this whole thing! Now they have a whole slew of people to go help because they were careless and they, of all people, should have known better. It also works because the recurring encounters with average joes aren't always going to turn out bad. The PCs have plenty of NPCs that they have befriended who didn't have anything terrible befall them.
in retrospect, you had a chance encounter that the players liked. You built upon it and the world was consistent. Then, when you needed a new plot hook, you created one that stemmed from their chance encounter and reactions. But to the players, you crafted a delightful twist to a story tha tmight have been months in the making. They feel like they could have stopped it if they had only looked for the curse to begin with. They feel like they need to fix the problem now because they care about the people, and they didn't prevent it from happening in the first place.
Obviously, this requires a lot of paying attention on the part of the RBDM. But with every encounter, every word that drops from the players, you are learning what they like, and what is working in your game. Then you are twisting the stories so they always revolve around the PCs. However, the world itself doesn't revolve around the PCs. There are always other things going on. But that is a different example and a different tactic that the RBDM uses.
