randomling said:
So what are the elements of plot building? What are the steps to building a good plot, and how do you get ideas in the first place?
Hmm. This is a tough question. To me: outlining and pacing are the two big parts of plot building.
My first thought is to turn to tv shows and movies your group enjoys- and begin to watch them as if you are watching an rpg game being played out.
Watch how the protagonists are introduced the machinations of the antagonists, and then the pattern for how that unfolds.
Different shows/movies tend to have different patterns.
Star Trek- TNG:
1) Become aware of antagonists (usually appears innocent)
1a) small side story begins, usually unrelated to plot, but runs parallel in theme and pacing to conclusion.
2) Conflict becomes apparent.
3) First attempt to deal with conflict fails and usually makes it worse, but leads to option for second attempt
4) Conflict spirals to near defeat of protagonists until second attempt succedes.
Simpsons (I love this example):
1) Simple short story of exploration or dealing with initial weak antagonist.
2) During the conflict- the protagonists begin to deal with true antagonist that has no ties with #1
3) Dealing with the major conflict takes the protagonists in a total unrelated direction from #1, and becomes the bulk of the adventure
4) Resolution tends to finish second resolution and the first (if it is outstanding)
Once you find a basic pattern that appeals to you- then you can begin to put ideas to it:
Simpson d&d adventure:
1) Players are sent to huge state-run library by their employer to retrieve book of family history, but the librarian will not hand over the book.
2) PC's run into distraught young woman who also is being refused access to a book she needs to save brother from the thief guild holding him.
3) PC's get involved in complicated plot to rescue a brother that does not exist- so the "distraught" woman can take advantage of the now weakened thief guild.
4) PC's get some recognition for (hopefully) dealing a blow to the thief guild, and can use some political leverage to get the book.
Now, I am not saying use this pattern every time. In fact, you should find a few patterns to try out and put aside a couple you can mix into a campeign.
Once you have the outline- you can then begin to flesh it out with encounters (combat and non). This leads into pacing- which is a touchy part of plot building. It only comes with experience- and knowing your style and the style of your players.
The last thing to keep in mind is that if you make an outline too inflexible (the players need to help the woman in the example abouve or the adventure is over), then the players will tend to break your plan. Not because they are being malicious, but because they don't always follow the dm's line of thinking.
You will need to think in terms of "what if" at times- when a pc decision is important. You can usually work branches of decisions back into the main story you have in mind.
For your last question- how do I get my ideas in the first place?
I usually steal them.
I buy many rpg adventures and supplements, and then pillage my way through the book for ideas I can use- perhaps just one room that I think is cool, or an npc I really want to use, or maybe a climatic battle I want to put the pc's in (this almost always backfires on me, heh).
A great source for ideas is the players- try to get them to write backgrounds for their characters and even summaries for adventures from their character's perspective. (I offer xp for both.)
Another way to use the players is once you have the rough idea of your world- lay it out for the players, and offer them the chance to write up parts of the world in exchange for xp. Religions, cities, countries, guilds, etc-
For example: I will usually come up with lists of countries, gods, guilds and etc- and put basic descriptions next to them. I will never write them fully out until I need them or a player wants to interact with them. So- if a player volunteers to write one up, then I have a resource to tap into.. and the player feels invested in the campeign when you use their creation.
Go read the Story Hour forum on this site. Just scanning them often gives me an idea I can use for adventures.
Good luck to you!
SD
edit: One piece of advice given to me by a great dm was that when running a campeign- keep track of what the players thing is going on. If they are totally wrong- but really excited with what they think is going on.. then go with it

The players like feeling clever and it helps you to have them excited with a story.