Life is much more interesting, and complicated, because people find other people attractive. Likewise with fiction. Our characters' romantic desires and the way they pursue them can tell us volumes about their personalities, not to mention create intriguing wrinkles in the fabric of our plots#&151;and the sheets!
So let's say that two, or more, of our characters feel some form of attraction toward one another. And it's mutual. And they have a time and place to do something about it. Should we have them melt onto a pile of silk-covered cushions in a flurry of caresses, then fade to black? Or should we describe everybody's body parts and what they do with them? Is one approach coy or even prudish? Is the other approach gratuitous?
In deciding how to approach sensuality in our own stories, it's helpful to consider the palette of sexuality encompassed by the genre, both past and present.
Once upon a time, science fiction stories shunned romantic involvement among the characters. When authors did include an element of attraction in a story, they treated it clinically, as though the protagonist could handle lust/love as objectively as any other obstacle to happiness. And, back in those days, protagonists were almost always male, women were usually problems to be solved, and non-heterosexual characters might occasionally be implied but were never heroes.
Fantasy, on the other hand, was more apt to deal realistically with intimate relationships. Tolkien, though appropriately chaste for his era, portrayed the bitterness of misplaced, unrequited love (Eowyn's for Aragorn); a man's efforts, ultimately successful, to win the romantic interest of an interesting but initially uninterested woman (Faramir and Eowyn); a marriage that is an ongoing romance (Tom Bombadil and Goldberry); and a marriage that is about raising children and creating domestic comfort (Sam Gamgee and Rose). Traditional fantasy plots often involve young people "coming of age" through having adventures, including romantic/sexual encounters. They also frequently deal with members of noble families for whom the pairing of offspring with appropriate partners is a major goal. ╩While romance and fantasy have been comfortable companions, a sensibility that fantasy stories were read by minors kept explicit sexual description to a minimum.
The Sexual Revolution changed everything. Read the Dangerous Visions anthologies, edited by Harlan Ellison in the 1970s. Read any author whose work spanned the before and after Sexual Revolution eras, such as Isaac Asimov. Writers suddenly had permission to explore adult themes, and they did--with a vengeance! Also, as more female writers--and a new generation of male writers--entered the field, dealing with relationship issues became much more acceptable.
S.M. Stirling's 2003 novel, Conquistador, features plenty of traditional gun-toting adventure in an alternative California, but of equal weight are the protagonist's developing feelings toward the woman who traps him there. In fantasy, Jacquelyn Carey's explicit explorations of S&M in her Kushiel's Dart series have gained wide popularity, as have Laurell K. Hamilton's steamy Anita Blake vampire novels.
The full range of human sexuality is now fair game, with more GLBT characters than ever, along with a full range of alien and alien-human sexuality handled with deftness and insight.
So when our characters feel hot and bothered, we have a full range of options available. We don't have to be explicit if we don't want to. We can be explicit if we do want to. Most genre readers will be accepting either way.
So what to do?
Fortunately, we don't need to handle sexuality any differently than we handle any other story element. We can use exactly the same criteria to decide how much space in the story and how much detail to devote to sex as we'd use to decide whether to describe what a character eats for dinner or what they talk about over the dinner table.
Characterization. We find out a lot about someone when we sleep with them. Likewise, our characters can reveal a lot about themselves if we let our readers accompany them between the sheets. For this to happen, however, we need more than a blow-by-blow description of tab A in slot B. If you're describing how a spaceship is put together, including lots of technical details can be interesting because most of us haven't built a spaceship. But most of your readers have had sex, so spare us the technical manual. It won't tell us anything we don't already know.
Instead, let your characters' approach to sex show us how they feel about themselves, how they feel about the person (people) they're with, and the mood they're in that day. In other words, we describe a sex scene for the same reasons we include a character's body language and dialog in any other part of the story.
Major Plot Points. A lot can happen during sex, or because of it. Jans can spot an identifying tattoo high up on the inside of Daria's thigh, but only if he's looking there. Mark can use a surprising and very pleasurable sexual technique to distract Everett from his partner's escape, but to buy that, the reader needs to know what technique Mark is using and just how much Everett enjoys it. Layla may get the first inkling that the queen's cousin isn't as shy and sweet as she pretends when that woman grabs Layla's wrists and bites her hard in the throes of passion. Onyx16 can discover that Beryl5.2 has a mysterious visitor in the wee hours every morning, but only if Onyx16 regularly spends the night in Beryl5.2's cocoon complex and is awake at that hour.
Sexual desire can be a great excuse for characters to go where they otherwise wouldn't and find out things that otherwise would stay secret. Again, lengthy descriptions of tab A and slot B may just bog down the story. If Onyx16 was on a stakeout in the web of Beryl5.2's cocoon complex, you probably wouldn't describe every boring minute of every boring hour. Likewise, with sex scenes, we need to know enough to understand why the story takes a new direction, but we don't need to know more than that. Get on with the story!
Highlighting Differences. Sexual activity is an ideal way to explore a pervasive theme in SF/fantasy: navigating difference. You might be writing a first-contact story about alien explorers and indigenous humans in which an Joolah finds a lot in common with Bob -- despite his ugly, scale-free skin and sunken, unstalked eyes. Or you may be exploring crown prince Rudolph's discomfort with power as he tries to initiate a relationship with a palace maid -- without being exploitative.
Whether your characters are struggling with differences of biology, culture, class, religion, etc., the sexual interface is one of the most powerful places to play out those challenges -- and opportunities. Don't be shy about giving us enough detail to understand your characters' complex, often ambivalent emotions as they move away from what's comfortable or socially approved. This is fascinating thematic territory.
Sex is inherently interesting. But that doesn't mean we can slack off and let sex scenes carry themselves. Sexual activity needs to be written with the same care we'd give any other part of the story. In particular: