Basic Story Structure

Knowing this is the key to successful DM'ing. Imagine it as if every episode were a TV program, with 'To Be Continued" at the end of each program. (Well, they are all like that, nowadays...)

So, at the beginning of each episode you need an introduction/recap to bring the player/s up to date: where they are, what they are doing, why they want to do it, etc. (Write this as the last thing you do after an adventure, it shouldn't take more than a paragraph or two.

Quote Originally Posted by brian 333
Example: Last time on Dragonball Z... err, sorry, I mean, When last we gathered there was a quest to discover why ogres have suddenly begun raiding towns, growing ever bolder. Some have surmised it is to gather magic items, others that there is a plan for total world domination afoot. However it may be, there seem to be more questions than answers.

Meanwhile, Daisy has found herself impossibly in love with Donald, whose vows of chastity and purity make him unapproachable, and thus ever more alluring. Thraxxar has found a scroll which could unlock the mysteries of higher magics if he could ever understand it, and with its guidance he may even achieve the awesome power of Level 4 Spells.

Now we find our intrepid band of heroes on the outskirts of Beldin, a small farmers' market town which, from the hilltop overlook, appears to have been raided by a band of ogres...
After the introduction we need to establish the evening's goal, as a part of the story. This allows the players the opportunity to investigate and discover what those goals should be, (or fall for a red herring and miss the goal completely.)

Quote Originally Posted by brian 333
The PC's enter the sacked town as the townsfolk clean up and prepare the funerals for their many dead, or care for the injured and traumatized victims of the raid. Affter meeting with the leaders they learn there is little enough in the way of food and supplies left in the town, the ogres having ransacked it, and that there are a couple of ogre prisoners the townsfolk plan to kill in revenge for their part in the battle.
Once the goal is established we need a buildup of pressure on the party, and they are forced to act lest the situation run out of their control. This could be combat sequences, but it could as well be social stress.

Quote Originally Posted by brian 333
Thrxxar and Daisy converse about Daisy's would-be relationship, and Thraxxar makes it plain that Daisy will have to choose between forcing Donald to break his vows or forcing him to break her heart. Will she choose either of these options, or allow her love to go unrequited?
Donald meanwhile interrogates the ogre captives, who are tough nuts to crack. How close to breaking his paladin vows must he go before the ogres finally reveal there is a hidden camp nearby that is used to spy on the town?
Then there is a climax: the ultimate challenge for the evening. This is the make-or-break moment for the party. Everything they have done so far leads to this moment, and its outcome determines the course of the next adventurer in the series.

Quote Originally Posted by brian 333
The band enters the woods and makes an attack on the spy-camp. It is heavily guarded, but not occupied by a true army. However, what it lacks in numbers it makes up for in quality. The spymasters and their slaves are tough opponents who challenge the party to their very limits! Removing these scum from the enemy's army will greatly weaken the enemy, but failure here could mean whatever survivors of the party make it back to civilization must recruit new companions if they wish to continue their quest, or abandon the quest altogether.
Finally, there is the ending, or denoument. This allows the party to learn the lessons of the event, split the spoils, and close up any loose strands that may be lying about, (or expose any hooks for the next installment.)

Quote Originally Posted by brian 333
Donald stands triumphant in the midst of the defeated ogre band. In his hand he holds a map, torn, but still legible, showing the locations of six other scouting camps, two of them outside towns which have yet to be sacked by the ogres. As he stands there he sees Daisy approaching, and cringes, knowing the effect he has had upon her, yet unable to find a way to resolve the situation. To his surprise, Daisy confesses her feelings, then says that her claims are selfish, that to remove Donald from his place at the head of the party at this time would be a disaster for them personally and for humanity as a whole. She will follow him as his soldier, and if after all this is over they both survive, will think about pursuing their relationship then.

Thraxxar screams with jubilation: he finally understands a critical piece of the formula and now understands the key to unlocking Fourth Level Spells! As he cavorts in joy the rest of the party gather what remains of the ogre's stolen wealth.
So,
I Recap
II Establish Goals
III Buildup
IV Climax
V Conclusion

Basic Story Structure.

Now you can have a little fun with it. The old time serials used to end right in the middle of the Climax and have the conclusion concurrent with the next week's Goals. They called this a Cliffhanger, supposedly because just as the hero was hanging from a cliff the narrator would break in with, "Will he make it? Tune in next week for another exciting episode!" The Adam West Batman series did this every single episode, in a conscious parody of the technique.

This is also the structure of an overall campaign. You may have many episodes in the Establish Goals section, a few in the Buildup section, and two or three Climax episodes, but within each episode there should be a stand-alone story. This gives the players a feeling that they accomplished something, and leaves them wanting to come back for more.

The structure helps you as a DM by defining for you what parts you must focus on as you build the night's adventurers too. Others have said to avoid planning ahead. I will modify that by saying, plan ahead, but not for what your players will do: plan for what your villains will do in each episode, and if the party hares off in the wrong direction you will know what the party can expect next week. The missing map, for example, that they should have found, will now be in the hands of the enemy who will use it. Next week's episode will be about catching up before the enemy wins the race!