Answering the system-agnostic tag I present you Empire Weather
The simple charts provide a glossary for seeding descriptions, accounting for prevailing weather, and an instant weather option as well. All using a single d10.
Belated Update... h/t @ryanfaescotland
Eight years and counting. I saw a recent upvote, and Ryan's comment. Yes I'm still using this chart. As recent as last week in my current D&D 5e in Greyhawk campaign (entering its almost fourth year!)
Dave Graffram simply makes it direct and with a dash of spice to make it setting relevant. IRL I had the opportunity to take a mountain hike that started off partly sunny. In the first 10 minutes of the hike, thunder. The guide said something witty about bear caves and trees being lightning rods. 30 minutes later, a thunderous downpour that lasted for the entire hike. Unprepared, the entire group was soaked to the skin. The trails became treacherous: roots and rock, covered in rain soaked bark and mosses, provided no perch for shoes. The hot day turned cool in the cloud cover and rain, then humid after the downpour.
I made a comment to my players in the following session about these experiences providing a frame for describing weather in the game, and justifying a liberal use of the Exhaustion rule in overload travel.
- Make the players invested in the history of the world. This depends on the system you're using. However, generally, you want the players to come up with a backstory, yes? Well, nudge them to tie their character's backstory in with the rest of the world. That way, when something happens in the world, they'll be emotionally invested in its outcome. Hence, direction.
- Design the world so that things happen. What it sounds like to me is that your worlds have a lot happening, but not much that directly concerns the players. If an optimally lazy person wouldn't be motivated to do something about it, you can't expect your (motivated) players to respond to it, either. There are a couple tricks to this, and I'm going to go into more detail below.
In order to create a world that engages the characters, Things Need to Happen. But even then, players probably won't respond to much unless they need to, so the Right Things Need to Happen. What constitutes a Right Thing?
- The Things have tangible, immediate impacts on the players. If they're motivated people, and they hear about a mysterious ghoul in the town next over who might enter their town, they probably won't do anything about it. They'll defer to that town to handle it, at least until the players absolutely need to respond to it. In this way, if the effect isn't tangible ("some of the peasants might get ill") or immediate ("if you don't head this off now, there will be serious problems in, oh, a decade or two"), they won't be engaged.
The Things must be something the player characters are invested in. If Matilda the Barkeep's husband has been captured the The Allthing of Evil, are you really going to care enough to venture to the Veil of Certain Peril and retrieve him from the Claws of Destiny? Probably not. Especially if you don't know Matilda, her husband, or don't really care about the town.
It is your responsibility to write the game for the players, as much as it is the players' responsibility to play your game in a motivated fashion. It sounds as if your players are definitely motivated, and they're looking for something engaging to do, but also that the game tasks that exist aren't really planned. Even though this is a sandbox game, the things that happen still need to affect your players.
"So, I've thought of something(s) relatively open-ended that their characters would be interested in tackling. What next?"
Think about it some more. Then think about it again. Then continue to think about it while you're playing the game. You need to consider in particular what the NPCs are motivated by, who they know, what they know, and what they plan to do about it.
Now, you don't need to know this for every NPC. However, the Special NPCs (SNPC, I call them, but that's a LARP habit), who drive the plot forward, create new twists, and are the NPCs who truly engage the players, need to have well-defined short-term and long-term goals, as well as basic personality sketches. Every NPC should have something(s) they can, with some difficulty, overcome, that prevents them from reaching these goals. These things should tie in to other players/NPCs/SNPCs.*
Throll has a long-term goal: he wants the Axe of Beldor, but unfortunately, it's buried beneath the Tombs of King Calthor. That wouldn't normally be a problem, except the Tombs of King Calthor happen to be underneath the city; in order to get to them, he must destroy several houses. Maybe of some people your PCs know.
He wants to use its magical power to destroy the peasants' rebellion. He has no qualms doing this.
When I say every NPC, I mean (pretty much) every NPC (though regular NPCs don't necessarily need to tie into the characters).
Matilda the Barkeep has a long term goal: She wants to build a second inn across the city. Unfortunately, she doesn't have the funds for it currently, as she was robbed by a mysterious bandit two days ago! Oh no!
Your players may or may not be engaged by this. If they're not, more options are needed. In a sandbox game, more options should pretty much already be there.
There aren't many SNPCs in a short game. Their motives are thick, and they are often (but not always) weak people. You only need a handful to make an interesting conflict. Give a bunch of twisted people power, and their scheming will stretch across cities.
The other type of NPC is the regular NPC, who don't get a fancy title or anything. They're just NPCs. These people need to have plans and know others as well, but theirs can be more abstract or simple. Your barkeep Matilda, for instance, could have a short-term goal of "I need to get more liquor." and a long-term goal of "This place needs some expansion." This alone will give your NPC more flavor, as they will be where they are for a concrete reason.
Just these two things will drastically improve your campaigns. To summarize:
- Get your characters to build a solid character background.
- Design the world so that Things happen.
- Make said Things concern the players, in a way which allows them to engage the world.
- Give your SNPCs complex and concrete motives. Give NPCs some minor motives on the fly. Some minor NPCs might know someone helpful.
- Let your players guide themselves through your story, and be free to modify it on the fly to match what they appear to follow.
This approach does make the game less of a pure sandbox, but will make it a more engaging sandbox, if a sandbox truly is the style of game your players appreciate.
*Side note: The difficulty and length of the game is often very closely related to how difficult the goals of the NPCs are to attain. Goals which are complex and will take a while to implement will result in a longer game; shorter goals, like Throll's, will make the game significantly shorter.
Best Answer
First, set up a Conflict Web. Start by setting up your factions that are involved, and why they are competing/conflicting. This is more to give you a set of motivations for any given group, leaders, etc. and allow you to simply improvise based on the group's needs/ambitions.
The Conflict Web is not static, it's a starting point. So you may easily see characters shift alliances or make temporary truces to accomplish goals.
Second, once you situate the PCs into the scenario, look at their goals, and likely problems they will face in terms of Logistics and Politics. This is effectively similar to how Apocalypse World produces "Fronts".
After each session, look at what the PCs attempted, who was affected, whether any NPC groups made major moves and figure out who is going to react and how. You can choose to update either the Conflict Web or the Logistics & Politics list, though I usually find myself only having to do serious updates after 3-6 sessions because it's relatively easy to track what happened with simple notes.
Both of these tools can scale up or down, so you can do intergalactic empire politics or the 28 guys stuck in a prison together, based on whatever fits your campaign.