When writing a quest/Campaign how much do you all write or plan for? Do you just have a list of things that the adventurers may encounter and work with it or do you all meticulouslay plan every detail and every outcome? Im finding myself planning ahead, writing every situation down and how to get around it and then bam! The players do something completely unexpected and I still have to make things up on the spot but because of planning I find that I’m trying to edge them back to my little already planned sections. Do you think of a quick storyline, maybe two or three sentences and see how it goes? Thanks, Luke. 

I try not to Railroad my PCs but I also meticulously planned parts of the campaign. But most of my planning goes into what specific NPCs are going to say and notes for how they will act. Also, descriptions of possible places that they will go to. I also plan out possible encounters and how to describe them. I try not to put  barely any of my planning into where the characters are going to go. I'd like them to go where they want to and do what they want to. There is an obvious general goal to the game and where it is going. But again I try not to railroad my PCs and make them go whatever way I want them to go because ultimately we are all playing a game together and forcing them to do what I want is not fun. 

For campaigns, I plan an overall outline of the story, with a focus on the beginning, the end, and any pivotal events in between. I think it's important to have at least an outline, to make sure you keep your campaign running smoothly. Having only an outline leaves room for improvisation and to determine how certain events occur. Having a more detailed plan can lead to railroading or other problems. Having too little leads the PCs to uncertainty and can make a story seem like nothing more than loosely-related threads that never amount to anything.

For adventures, I plan in much the same way- a clear opening scene and end and a few important scenes in the middle. But one piece of advice is to make you sure you leave all your scenes open-ended. For example, if one scene is an audience with the king where the PCs seek to win the king's favor, don't assume the PCs will succeed or fail. Just let things play out based on the king's personality, motives, and goals and the particular approach the PCs take. Better is to plan for a few contingencies: what will the king do if the PCs insult him? If they reveal they know some damaging secret about him? And so on.

If the PCs reject your plot hooks, or take a wrong turn, or fail disastrously in some way, let them. But give them an opportunity to make up for their failures. Maybe this causes an adventure to lead in an unexpected direction, but as long as this eventually leads back to the events you outlined for the campaign as a whole, it shouldn't greatly affect the narrative. This way, the PCs get to choose their path but there's still a clear, overall storyline.

Since I'm getting back into it we're running mostly adventure modules. Which are turned into a campaign with the same thematic elements. To make them fit together you do the same as I used with homebrew. Look at the big picture and the broad strokes. Some key moments/events you want to happen in your world. Then you try to rationalize how they would fit together. Once you have that you can add some more detailed key events/areas, but still keep it broad and generalized. This basically lets you move those events whereever the players decide to go to.

Then you prepare the broad strokes towards the first key event you decide upon. Once again create some smaller key events along the way. Prepare a city/vilage/overall environment for the first bits. Some random encounters, sprinkle a few quest hooks around of which you prepared some broad strikes of events/outcome. Then play and make most of it up on the spot. Once you get a feeling how your group plays you know how many events in advance you have to prepare with more detail.

With the pre-made module I expected the group to play at least upto killing the first baddie. Instead they spend 3 hours investigation dead ends in town. Meaning my prepared content can last me for 3 more sessions at this pace :P

So, I didn't get a chance to answer this before someone brought up railroading in connection with planning. So now I am forced to beg the OP not to listen to anyone who thinks that planning is railroading on any level!!! That isn't because you should railroad your players, because railroading is bad! It is because they don't know what railroading is. They think they do but they don't. Here is the thing about planning, you are always planning, always! Even when you improvise you are planning, you are just planning about 1/10th of a second before you put the plan in motion...OOOHHH it looks like those of you DMs that are improvising are just railroading your characters! Bad DM! Can you see how the planning is railroading argument is stupid? Yes...good! Now, that we have all of that out of the way. You should plan only as much as you need too. If you are good at improvising NPCs but not at making up the locations then you should focus on pre planning locations. If you are good at whipping up a top notch combat but shaky on backstory then focus on building the backstory you need before the game...etc. etc. The problem with anyone telling you what they do to plan or prep is that they aren't you and you aren't them. They have their own strengths and weaknesses and they probably won't be the same as yours. If it sounds like I am telling you this is something you have to figure out for yourself, it is because it is and I am. Sorry you can't copy off my notes...life sucks, get over it.

• The group has finished their challenge
• Nailo accepted a job to escort a caravan to the Dwarven stronghold
• Group meets the Half-Giant merchant train
  • Shopping opportunity: x2 to potion size/uses per 
  • Insight (15) wife is nervous, could learn about kidnapped daughter
• Avarist must persuade Dwarven guards to allow the group to enter
  • Difficult due to estranged brother
• Kidnapped daughter
  • Band of mercenaries is using the half-giants to gather information about nearby settlements
  • Mercs work for opposing country
  • daughter is starting to agree with mercs ideologies

 That is how I plan every session, adventure, and campaign. I take notes from every session, make bullet points to give a flow to the way the world is turning. I have every plot and story arc set up with the same bullet points. In the case of plots/story arcs I have 2 end states; success and failure. This type of ending allows me to adjust what happens if/when the players finish any of the many plots and story arcs going on in the world. This type of layout also allows me to keep the timeline, making sure that as the players continue to act, the stories continue to happen. I'm also able to add bullet points to the list so that I can personalize different things based on player actions.

I have gotten to the point where I plan in a few ways simultaneously now, but it really comes down to:

1. Have a well defined plot structure/flowchart that the party can follow; but don't expect, or force them to follow it.
   • Sketch out the most likely series of events, with branching points where the plot-line would change depending on the outcome of each encounter or event.
   • Define transitions on how the party gets from this encounter to the that encounter; have several of these leading out of each encounter, and several leading into each encounter. 
2. Have means of improvising new series of events outside that structure in response to unexpected actions the party takes: You are unlikely to plan for every possible transition out of an encounter, so know what will happen when the players invent a transition you didn't anticipate ( rather than telling them that they can't do it :p ).
   • Know all the agencies involved in the current situation, with their goals, abilities, limits, and personalities.
   • Be aware of timed events which will happen regardless of what anyone does ( i.e. the storm hits the port city on Thursday ).
   • Evaluate what each agencies would do next in response to the unexpected party actions, or events.
   • Extend/replace parts of your plot flow defined in #1 ( even if it's just in your head, and one step ahead of the party ).
3. Have means of nudging - but not forcing - the party back onto the default structure ( or parts of the new structure you sketched out in point #2 )  if/when the party goes off on a tangent, gets bogged down, and doesn't know what to do next. I usually have these with an associated cost to the party ( the mysterious strangers who sat down at your table unexpectedly says "I understand you're looking for information about ____, I might be able to help you, but I'll need something from you in return ... " )

This is kind of like creating the transitions in point #1 that don't start anywhere, can start completely randomly ( or at DM discretion ), and point into an encounter that you created originally as part of your plot flow, or that "came into being" as a new possibility in response to unexpected Player actions.

This combined approach allows "spectator" players to just drift along the default structure, if they wish - but allows active and dynamic players to go off script, and do whatever they want, without the DM getting totally befuddled, and allows the DM to rescue the narrative if the party "paints themselves into a corner" and doesn't know what to do next.

In a perfect world, with genius Players, and a genius DM, you could rely solely on the second part, but truth is that some players don't want to work that hard or that creatively all the time, and would rather select from a handful of presented options ( or some variant of them ), and DMs ( or at least me  ) create better encounters with planning and revision than solely "off the cuff" all the time.

I also make it clear to my players that "fate" ( i.e. the GM ) is likely to reward innovation and creativity; that following the obvious default path is the easiest, not always the best  ( I'm still struggling with that one; it's absolutely DM meta-gaming; not sure that's a bad thing here ).