First of all, this whole thing is pretty much a slight variation on this.
I'm running a city and my first thought was to adapt Vornheim's encounter table to the setting and go from there.
The thing is I don't always know what to do with the Vornheim encounters. I'm not going to call it a flaw so much as a certain capacity I lack to resolve the specificity of those situations with the bigger picture of my game. When I try to run those encounters it tends to feel like a non-sequitur. Too many of those in a session and my player's eyes begin to glaze over as I urgently try to make this thing I just rolled on a d100 seem interesting to them, rather than a weird intervention in whatever it was they were already trying to do.
So instead, I came up with this:
Whenever the PCs are travelling from one neighbourhood, or at whatever interval seems appropriate, roll 1d6:
1-2. Answer a city question
3. Dangle a hook
4. Pull a string
6. Draw attention to a PC.
Answer a City Question
This usually just means describing the scenery as the PCs pass through. You can make it interesting but it doesn't always have to be. This can also be a short (like, 3 sentence) lore dump. It's meant to make the city feel more alive.
Roll 1d20 and describe a situation that addresses the question.
1. What kind of people live here?
2. Under what conditions do they live?
3. What is the local food like?
4. What is the city's topology like?
5. What kind of government is in place?
6. What role does the law/state play in daily life?
7. What is bizarre or unique about this city?
8. What roll does magic play here?
9. How does crime figure into daily life?
10. What strange goods can you purchase here?
11. What kind of tensions are in play?
12. Is violence common?
13. What threats does the city face from without?
14. What lies just beneath the surface?
15. Who really has power?
16. What role does religion play here?
17. What is the local religion like?
18. What is this place's history?
19. What kind of influence do celebrities have?
20. Who or what is popular, famous, or fashionable?
You can prepare answers to these but the idea is you don't have to. If you're stuck on a question, make a note of it and roll again. Make sure to come up with an answer by the beginning of the next session.
In a city with a variety of different neighbourhoods, this also tells the players more about this particular area.
Dangle a Hook
Try to have a short list of 3 or 4 adventure hooks on hand. A hook is evidence pointing to a source of adventure, treasure, XP, etc. The ones I have ready are a magical circus coming into town, an elvish dandy who's seducing people and robbing them in front of their faces, but has enchanted his identity so as to be unrememberable; a duelist with a magical sword seeking challengers; and a rad circus/light show coming into town soon.
Hooks should be prepared enough that your players can start pursuing them instantly if they're interested enough, but distant enough that they don't have to. In other words, they don't feel forced to bite.
In game terms, a hook is often presented as overheard gossip or an event witnessed from afar.
Pull a String
Strings are situations in which PCs get involved but don't necessarily see through all the way. They tend to just happen as a consequence of the way players act. For example, last session my players lost control of their Blink Dog and it killed a member of some new cult. Any situation where you think, "there could be more to this," creates a string. Also, a hook that players show an interest in, pursue, or investigate partially, might become a string.
When you pull a string, you remind the players, directly or otherwise, that the string is still in play. So in the cult's case it could just be murmurs that they're growing in number, a run-in with angry cultists who witnessed the attack, or full-scale retribution from the cult. Generally, it's a good idea to let things escalate gradually. When in doubt, I make a reaction roll for the interested parties and/or the Universe.
Alright, this is a non-sequitur. Here's where I'd probably roll on Vornheim's encounter table, or on one of my own making. It presents a situation that usually demands some kind of intervention from the PCs, but that they probably weren't expecting and that isn't necessarily related to other things going on. This might generate new strings.
Draw Attention to a PC
This presents a situation that addresses a PC in particular. You can choose one at random, but my approach would be to turn to either a) a newer player of b) on that hasn't spoken much this session.
The idea is to present some kind of situation that will bring one character in particular to the fore. If there appears to be some kind of tension between a few PCs, this could also serve as an opportunity to exploit that tension by bringing in something relevant to both of them.
If you can't think of anything to do with this, roll a d10 on the Character Questions table below. If the result doesn't give you anything to work with, ask it to the player directly. If you've asked it before, put a new spin on it or ask for more detail. Present a situation that makes the given answer relevant.
1. What is your family like?
2. What are your friends like?
3. What was your greatest achievement?
4. What do you believe in?
5. To what do you aspire?
6. What are your flaws?
7. What are your virtues?
8. Who are your enemies?
9. What was your home town/neighbourhood like?
10. What has been your greatest failure?
The outcome might be as mundane as the player describing an old friend, and you tell them that, despite not having seen them in years, that person is right there across the street. If the character is a recovering alcoholic, there's a bar doing an all-day happy hour promo and glasses clinking loudly. That can be enough.