Simply ask yourself a series of questions and draw a card from the game...
-Who is hiring the PCs? Draw a Lord of Waterdeep card.
-What is the known part of the quest? Draw a Quest card.
-What is the hidden part of the quest? Draw a second Quest card.
-What is the complication/twist? Draw an Intrigue card.
-Who is opposing the PCs? Draw a Lord of Waterdeep card.
From there is just a matter of combining the various elements into a cohesive adventure. Here is an example of how you can piece it together...
-Who is hiring the PCs? Nindil Jalbuck - A doppelganger posing as a halfling priest. Piety and Skullduggery.
-What is the quest? Raid on Undermountain- "Mount an expedition into the dangerous depths of Undermountain, and untold riches will be ours."
-What is the hidden part of the quest? Procure Stolen Goods - "Marune the Masked, one of the Shadow Thieves, needs to move some interesting merchandise."
-What is the complication/twist? Free Drinks - An attempt to waylay a person.
-Who is opposing the PCs? Sammereza Sulphontis - Trade Lord with Commerce and Arcana.
Nindil approaches the PCs, likely in another guise. He claims he is looking for something specific within the Undermountain, likely a magical legacy of a god. In truth, he owes Marune a favor and is picking up some goods within the Undermountain and transporting them into the city to clear his debt. With the Undermountain being as dangerous as the rumors state, Nindil has decided to hire some adventurers to clear the way.
However, Sammeraza has gotten wind of the expedition; Marune is one of the competition. On the night before the party is to leave he casts a spell on the drinks and food of the party that will cause them to fall into a deep sleep, which will in turn cause them to miss the expedition and anger Nindil. He is hoping this will forestall the movement of goods. If the characters can overcome this attack, you have a dungeon crawl to run!
Obviously, this works best if you are running a campaign in Waterdeep, simply because you won't have to change any of the names around. But really, it can work in just about any campaign. Just take the archetype of the cards and apply it to your own campaign setting. If you draw a Lord of Waterdeep card that calls for Piety and Skullduggery just use one with similar leanings in your own world. Essentially boil down the card to its base form. Using the sample adventure...
-Who is hiring the PCs? A doppleganger posing as a priest.
-What is the quest? Raid a local ruin.
-What is the hidden part of the quest? A master thief is using the ruin as a storage location and wants the goods moved.
-What is the complication/twist? Poison the PCs.
-Who is opposing the PCs? A smuggler that is also a magic-user.
With 60 Quest, 50 Intrigue and 12 Lord of Waterdeep cards there are many combinations available for creating a variety of adventures.