After you've found a clear objective for your characters (or, more aptly, helped them find one for themselves), the next question you ask is the root of all adventure: Why haven't they already done it?
If the answer is simply "Because they haven't gotten around to it yet" then odds are good you're about to go on a very boring ride. Good stories and good games start with some barriers between the beginning and end. This is so easy to illustrate in games - Imagine a a game where you just win, with no challenges to players or characters - that it's almost uninformative. If a caper could be resolved by simply walking in and walking out with the MacGuffin, then Ocean's 11 would be the most boring movie ever. 
Stories have a few advantages in dealing with these obstacles that games don't - whatever actions the protagonists take will probably help solve the main problem. I've mention this before in the context of B-plots. The A-plot (the main goal) can't be resolved until the B-plot is resolved because the B plot gives the tools necessary to solve the A plot. This is a useful tool, and KWORC refines it a bit with a bit more structural focus.
When you ask why the heroes have not already achieved their goal (either in a sweeping campaign or a single session) then the answer is that they lack something essential to success, and that something is one of five things: Knowledge, Will, Opportunity, Resources or Capability.
Let's look at a murder mystery to illustrate how these might come into play. In a classic closed mystery, where the detectives have arrived and all the suspects are in one place, the only thing the characters lack is knowledge. Once they know who did it, achieving the goal (arrest the murderer) is easily accomplished.
Suppose they figure out who did it, but the guilty party is powerful and dangerous. She's someone who can end the character's careers, kill their families or otherwise make terrible things happen to them. Alternately, she may offer them a rich reward to look the other way. In either case, characters are capable of achieving their goal, but the question is whether they have the will to do so.
Similarly, suppose that they identify the culprit, got to arrest him, and discover he's made a break for it. If they can catch him, they can arrest him, but they need to catch him first to have the opportunity to arrest him.
What if the culprit has his own private army, and is fully capable of refusing the request of a few detectives to come along with them quietly? Or if he has friends in city hall that make an arrest impossible or pointless? The players may not have the resources to make the arrest
Lastly, while this rarely happens in detective fiction, it's pretty common in RPGs for the culprit to put up a fight, and for that fight to be pretty nasty. There may be some question regarding whether the characters have the capability to make the arrest.
Now, there may be only a single such barrier between the characters and their goal, or there might be several, related or unrelated. Whatever the case, the utility of breaking them down like this is that you create a discrete set of obstacles. This is important because each obstacle creates an implicit goal - OVERCOME THE OBSTACLE. And with that in mind, go back and ask the first question, and you can produce another KWORC breakdown. Repeat this as many time as you need, and you have a picture of how an adventure is likely to unfold.
One more dirty trick: This is not just a GM technique. Players looking to find a way to make concrete progress on their goal can perform a similar breakdown of their situation to attempt to determine what concrete next steps they can take.
Right now this is a pretty rough model, but it's possible to polish each of the steps to really bring it to life. And that starts tomorrow with the anti-KWORC.
1- Curiously, the level of challenge is also often tied to the nuance of the goal. Using Leverage as an example, it's a show with hyper-capable characters pitting themselves against unsuspecting bad guys. If their goal was simply to _punish_ the bad guys, then episodes might be mildly cathartic, but they'd be ultimately hollow. All it would require would be that something terrible happen to the bad guy. Because their goal is _justice_ they put themselves in much more difficult situations than they have to. This in turn makes their level of capability feel appropriate (because it's challenges) rather than shooting ants with a howitzer. Does this mean your goal can actually be a basis for obstacles? You betcha.
2 - Thus, KWORC. It's not a great acronym, but I ended up using it because it was easier than checking my notes every time I needed to remember all 5. I'm sure that someone's going to suggests a really compelling 6th at some point an it will totally mess it up.
3 - Opportunity often pairs with other obstacles to be anything but a short-term obstacle. If the opportunity I lack is that I'm not in the same room with the guy, that's only a problem until I find him. For this to be a longer term problem I might not know where he is (knowledge) or have the means to reach him (resources). Despite this, this is an important category because this is what the Dungeon represents at its most basic level. You can beat the end boss and get his loot, you just need to _get_ there.
4 - For example, In the Lord of the Rings, destroying the ring requires opportunity (Getting it to Mount Doom) and Will (the will to get rid of it).