Organic vs. Outline

There are two general approaches to starting the writing process: outlining and organic writing. Both methods have advantages and flaws. Many writers use some combination of both. Which is best? The answer largely depends on the writer, but this brief overview should help.

Outlining
The writer undertakes extensive world building and planning before drafting begins. The overall story structure; plus major characters, themes, and plot twists, are outlined.

Advantages

• Reduces the likelihood of omitting important characters/scenes/plot points, etc.
• Gives the writer a road map to fall back on if the story goes astray.
• Theoretically speeds up the actual writing process, which can become as simple as filling in the outline.
• Minimizes the risk of wasting time and effort by becoming disenchanted with the story after writing several chapters.

Flaws

• Can delay the start of writing by encouraging endless world building.
• Promotes excessive exposition on background concepts like magic systems, fantasy world history, character origin stories, etc.
• Runs the risk of turning the art of writing into a sterile, paint-by-numbers exercise.

Popular outline writer: Brandon Sanderson

Organic/Discovery Writing
The author gets an idea and just starts writing about it, letting the story develop organically.

Advantages

• Minimal risk of writer's block due to incessant world building.
• Easier to make changes rather than scrapping a whole story.
• Greater freedom to "follow characters" who take the plot in unexpected directions.
• Lowers the risk of scenes/characters/plot twists feeling forced.

Flaws

• No reference to fall back on. "Working without a safety net".
• Easier to forget important concepts/plot points.
• Increased risk of writer's block from lack of direction.
• Greater chance of a meandering, bloated narrative.
• Avoiding flow/pacing problems takes strong self-discipline.
• Higher risk of continuity errors.

Popular discovery writer: Stephen King

For a more in-depth treatment of this subject, Writing Excuses has an excellent discussion on discovery writing and several on outlining.

Faith in Fantasy

Religion is one inevitable aspect of world building that is perilously easy to get wrong. Readers are culturally and historically conditioned to expect that faith will play a significant role (implicitly if not explicitly) in any fantasy universe. This convention is no less true of science fiction, though it more often operates in the subtext.

I find that fantasy religions are most often mishandled when authors invoke the cliche of transporting primary world religions into their fictional settings with only minor linguistic and aesthetic tweaks. Unless logical reasons are given for how a belief system whose cult, code, and creed exactly mirrors that of a real-world faith developed, this approach strains suspension of disbelief.

Worse, the temptation to make a fictionalized version of an actual religion into a straw man embodying an author's pet grievances can be hard to resist. This offense is sometimes committed knowingly, but more often it results from a lack of diligent research.

Not that designing fantasy religions from whole cloth is the only--or even the best--way to create credible, organic-feeling faiths. Fabricating belief systems utterly alien to the reader's experience likewise inhibits immersion and suspension of disbelief. It's important to provide theological and cultural touchstones with which readers are familiar.

Therefore, the best advice I can give to writers crafting a fictional religion is to study primary world faiths. Choose your sources carefully. Avoid histories written by obvious detractors of a particular creed who likely have axes to grind. Give preference to primary sources within the faith's tradition written by members in good standing.

As for creating fantasy religions, a brief overview of the basic categories into which nearly all real-world creeds can be grouped should be helpful.

• Philosophical/Civil: straddling the line between religion as such and ethical and juridical systems, these traditions can be effectively agnostic while accruing ceremonial trappings. Examples include Confucianism, Taoism, and some Aristotelian and Platonic schools.
• Deist: deism acknowledges a creator, but one so transcendent as to rule out communion with humans. The Deist God is a "watchmaker" who sets creation in motion and walks away to let history play itself out. Many influential Enlightenment figures held this view.
• Pantheist: almost a negative image of deism. Pantheism denies God's transcendence, locating divinity in all things. In this view, The universe itself is the supreme being, and all its constituents share in the divine. The pantheist cannot truly speak of creation, since nothing exists that is not God. Pantheist thought can add an interesting angle to a story's morality since it sees good and evil as equally valid aspects of the same reality. Shinto and some aspects of Hinduism are pantheistic.
• Polytheist: though it also denies the transcendence of divinity, polytheism doesn't divinize the whole. Members of classical polytheistic pantheons are portrayed as the offspring of natural forces, so they aren't eternal and usually aren't said to have created the cosmos. Such gods differ from men in degree of perfection more than order of being. Polytheistic faiths are fantasy mainstays but require care to avoid being portrayed as caricatures.
• Dualist: dualism posits the existence of two supreme beings: almost always one good and one evil. Dualist theology usually develops as an attempt to address theodicy, or the problem of evil. In this case, all good things are credited to the benevolent God, while all evils are ascribed to the malevolent one. Manicheism is a notable dualistic faith. Dualism is also wildly popular in fantasy settings, e.g. George R. R. Martin's R'hllor/Great Other.
• Monotheist: the belief in one, eternal, transcendent, and immanent supreme being. Though deism professes a single Creator, it is a dependent offshoot of the Abrahamic faiths which view God as transcending creation while remaining active in it. Though often epitomizing evil in a Satan/Adversary, monotheism differs from dualism in that this evil agent is not a god, but a corrupted creature. Also common in fantasy settings, monotheistic faiths are especially at risk of distortion since their real world prominence leads some authors to take incomplete or false understandings of their creeds for granted.

World Building

All fiction genres share the same building blocks. They must have protagonists, antagonists, a goal, conflict, and themes. Only science fiction and fantasy add a step to these elements: world building.

In my experience, shoddy world building is the second most common cause of poor storytelling right behind underdeveloped characters. Some people harbor a naive view of world crafting in which rewinding time to the bronze age and introducing dragons suffices to ground a fantasy setting.

Much like writing believable characters, solid world building takes finesse. If the structures and rules of your secondary world depart too far from the reader's experience of the primary world, you risk breaking his suspension of disbelief.

On the other hand, an effective fantasy world must be able to foster and maintain escapism. Offering the reader vicarious adventure beyond the confines of reality is the whole point of speculative fiction. So the setting has to include at least one major exotic element: magic, geocentric cosmology, androids, FTL travel, etc.

Creating a sound secondary world is a tightrope act. Lean too far one way, and the audience can't relate. Lean too far the other way, and the setting becomes too dull to hold their attention. The best way to avoid both extremes is to lay a foundation of internal consistency.

Figure out how your secondary world most differs from the primary world. Is your world separated from ours in time? Is it another planet in the same universe? Is it in another cosmos altogether?

The answers will indicate how much your world's rules may differ from those of the primary world. (For example, since my fantasy setting is located in another universe I avoid using words derived from earthly people, places, and events.) Once you've set these standards, don't deviate from them unless the change results from natural story developments. Much like symbolism, world building is most effective when readers don't consciously see it.

That's my approach to world building. What are your picks for best/worst designed sci fi/fantasy worlds?