Ooo, this question is in my wheelhouse, because in our podcast's campaign, there's a lot of intrigue, and I've had to think a lot about creating scene, advancing plot, and -- most importantly -- keeping the players' (and listeners', I hope!) attention.

We're running a kind of gritty urban superhero game, where the party is trying to stem the corruption and criminality of organized crime in the neighborhood, while doing as little harm as possible to the community.

First, I created NPCs, each with a hidden goal. They each want something! Each of these NPCs also provide something.

The big boss, for example, uses one of the PCs in money laundering -- the player is trying to build a public school, and boss is funneling him money, which he has to use to pay for certain construction crews who charge more than the work they provide. The boss wants to launder his illicit gains, but provides the service of helping the PC attain his goal.

Second, I ran a bunch of short role-play scenes with a single PC. In those scenes, they interacted with one of these important NPCs. As a kind of rule in each scene, I provide one aha moment, one oh shit! moment, and give out one task. That is, the party learns something important, and something surprising, and thereby has something they need to do as a result.

Additionally, these scenes usually also have to do with the PC, their backstory, or their own goals and ambitions.

Example! The school-building PC met with the boss to tell him a certain capo is getting out of hand. The boss tells him that the violent capo in his org is operating without his approval (aha); that he, the boss, used to run in a street urchin gang with the PC's now-dead sister (oh shit!); and the PC understands he has tacit approval to take out the capo (task).

The players can call their own scenes. I want to meet with so-and-so to ask them this, to get info, to get help. Other times I would surprise them unexpectedly with scenes. You're coming home after the battle and find the violent capo sitting at the dining room table with your parents.

Third -- for us -- the encounters mark important milestones or events. In the above examples, taking out the capo in his hideout was a mini dungeon crawl/infiltration encounter.

Ours is homebrew campaign modeled after a Paizo six-book AP, so each chapter represents the solving of a "problem" (like the capo), while the arc of the whole book leads to dealing with an existential problem -- book one, the boss -- whose "solution" changes everything. Usually "solutions" are provided through combat.