As there appears to be very little advice out there on writing heterosexual sex scenes, I thought I’d take a stab at it. This is meant mainly for M/F scenes, but much of it applies to slash also.
Many of you may think writing sex scenes is easy. Nothing could be further from the truth. While anyone can throw a few sentences together describing a sexual act, writing a good sex scene that is erotic, emotional, involving, and convincing in terms of characters and physical realities is surprisingly difficult. Just the terminology can be a challenge, not to mention avoiding clichés and repetition, and in the case of slash making it clear who’s doing what to whom.
Now the usual question, who am I to be writing this? I’m a huge reader, and have read my share of erotic fiction, including fanfic. I’ve also written it, although only two of my NC-17 scenes have made it to a cringing public. Also, when it comes to the real thing, I’ve read about it from scientific sources, can speak from personal experience, and have discussed the topic with various friends and more-than-friends over more years than I care to admit to.
What are You Writing, and Why?
Take the time to answer this question before you start. Are you writing porn, something that exists solely to be sexually arousing? Then, besides writing style, all you need to worry about is keeping your anatomy fairly correct, so you won’t provoke laughter instead. Are you doing erotica, a story about fully-developed characters that happens to include explicit sex? Then you’ve got all the headaches of writing any story; having some semblance of plot, good characterization, etc. Are you writing a non-explicit love scene? These can have much of the story impact, and many of the challenges, of more explicit scenes. What you write depends on your taste, the purpose of your fic, and hopefully the demands of your plot.
Erotica may be a PWP (Plot, What Plot?), in which case you don’t need much of a story, but you still should set up a situation that convincingly gets your characters in bed. It may also be explicit scenes included in a longer story. In either case, erotica is, in my opinion, one of the hardest forms of fiction to do well.
Part of your decision will be exactly how explicit you want to be. A lot of fanfic writers seem to think hot sex scenes are expected of them, that readers will be disappointed without them. I disagree. If you aren’t comfortable doing this kind of writing, or feel uncertain about the quality of it; if you want to reach a more general audience, or feel that explicit sex doesn’t fit with the story, by all means do a fade-out before the body parts come into play. Many readers actually prefer it that way, and it may be better for the quality of your stories. While sex scenes used properly can show intimate details of a character and a relationship, all too often they simply bring the plot to a screeching halt.
You also don't have to write something explicit in order to write something erotic. The most important sexual organ in the human body is the brain. Suggestion, the description of a character's emotions, reactions, desires, sensations, writing that has us sharing those feelings... The reader's imagination will supply the rest.
Most of the rest of this page is rated somewhere between PG-13 and R; there’s some frank discussion of sex, but nothing really explicit. If you’re underage, please leave now.
Realism - How Much? What’s Realistic, Anyway?
They say to write what you know. I’ve read some smut out there that made me strongly suspect that the author has never - or almost never - actually had sex. If this is your situation, it doesn’t mean you can’t ever write a good sex scene, but I think it does tilt the odds against you; I really think experience counts for something in this area. The sensations of sex, the feel of another body, the smells, the sounds, the mixture of intense emotions; even the clumsiness and the messiness; these are the kinds of things that have to be experienced firsthand, and that contribute to writing scenes that are both original and believable.
That said, I don’t want to discourage anyone from trying. Everyone old enough to be writing a sex scene knows how it feels to be attracted to another person, and to be aroused, and can use imagination - and some research - for the rest. Also, you don’t have to have experienced every act you write about, or women would never be able to write slash.
Fiction doesn’t have to be strictly realistic. You may not want to deal with safe sex, or bodily functions kicking in at inappropriate times, or who gets to lie on the wet spot. You probably want to write sex that’s better than the real thing, which can be messy, embarrassing, uncomfortable, and unsatisfying. That’s all fine, and in fact many readers prefer idealized fictional sex.
However, I personally cringe at fics that are blatantly unrealistic or depend heavily on clichés, and you’ll lose your readers quickly if it sounds like your characters are doing something physically impossible. So here goes, with a few basic facts and guidelines, based on the non-realisms I’ve most often seen in fanfic. How much realism you want to actually apply is up to you.
This kind of thing can be fun, and provide variety. However, you’ve got to consider whether your character would trust the other person(s) enough to, for example, let themselves be tied up. In real life, most people are more likely to indulge in such things with a steady sexual partner or a long-time friend with whom they feel very comfortable, but - everybody’s different. Be aware that showing someone leaping into an unusual sexual act with a near-stranger will say something about their personality. So, don’t be shy, but keep it in character.
However realistic you want to be, there are a few rules it’s always best to follow:
Make sure your characters have the proper number of arms and legs, and other appendages, at all times. Don’t describe an act or position that would require three hands or two heads or other body parts in the wrong place.
Don’t put the characters in impossible or extremely convoluted positions. It’s a turn-off to have to stop and try to figure out what’s going on. Make sure they’re facing the right way for the act you’re describing. Visualize the positions, make sure they’re possible, and describe them briefly but clearly. If they change, tell us.
Emotion
What emotions are your characters feeling when they make love? What are they feeling before the act? During? After? This aspect is more important than the mere mechanics of sex, which don’t vary all that much. (Unless you get kinky - and even then...)
I’m not necessarily talking about love here. You may be writing about characters who don’t love each other, don’t know each other, have just met, actively dislike each other but have a strong physical attraction, etc. There are all kinds of possibilities.
Now - a lot of this gets back to the question of realism. You don’t have to be 100% realistic, but a reader should be able to get through your fic without total, outraged disbelief. So, you need to stay in character, and be aware of basic human nature.
Love. It almost always takes time. Even what seems like love at first sight needs some getting-to-know-you time to become real and solid. Otherwise, it just fades into a forgotten attraction that never worked out.
Overly fast movement of a love relationship between characters who have just met is a very common problem in fanfic, and I think I know why. The author knows the characters very well when he/she starts writing a romantic story. They are, for the most part, either a favorite canon character or some degree of a Mary Sue based on the author him- or (usually) herself. The author knows these characters are perfect for each other, knows they’re meant to be lovers (in the fic, anyway). In his/her eagerness to get the characters together, the writer forgets that they do not in fact know each other in the context of the story. The result is two characters meeting for the first time, admiring each other for a chapter or two (or even just a few paragraphs), immediately jumping into bed, and declaring eternal love as soon as they’re done. Not realistic at all.
Think about your characters. Are they the type to have sex with a virtual stranger? Are they foolish enough to think they’re in love right away? Such things do happen, but will they happen to your particular characters?
Some basic facts: Men (in general) are faster than women (in general) to have sex with someone they don’t know. (Like you need me to tell you that.) Men (in general) are much less likely than women (in general) to see any deep meaning in the sexual act or to decide they’re in love with a woman (or another man) just because the two of them have had sex. (Ditto.) There’s huge individual variation, of course, plenty of women indulge in casual sex, plenty of men are reluctant to. Circumstances have a lot to do with it. Danger or an intense shared adventure may well make two people feel much closer than they actually are.
It usually makes a better story when you build a relationship over time. Let your characters get to know each other. Talking is important; make sure the reader sees that they have something to talk about, and that they care about each other. Ideally there should be clear signs that they love each other long before either one of them says it, and ideally your readers should want them to get together long before it actually happens.
Of course, you may be starting with characters who have a relationship, sexual or otherwise, in canon. A lot of the same rules apply if you’re taking them from a friendship into a romance; it’s going to be a new side to their relationship and they (and the reader) are going to have to adjust to it.
In any case, try to understand your characters, and don’t make them do something wildly different from what we’d expect. Don’t have a tough, cold, unemotional person suddenly turn into a weeping romantic. Don’t have an innocent, inexperienced young person suddenly diving into all kinds of unusual sexual acts with uninhibited enthusiasm. (Even more important, don’t show him/her being an expert at it!)
Another big tendency in fanfic is over-romanticizing. Most men are unlikely at any stage of a relationship to make flowery speeches or compose love poems in bed. Hell, with most men it’s tough just getting an occasional ‘I love you.’ None of which means they don’t feel love, and feel it strongly. Women also, while more likely to talk about feelings, don’t generally go on and on about it. Keep your declarations of love brief, subtle, and infrequent; they’ll mean more.
Now we come back to the point I was making in the first place. Most people, male and female, do attach strong emotions to having sex with someone they love. Including those emotions in your sex scenes will give them impact and depth, beyond just body parts interacting. Don’t go overboard, but show us what they feel - and show, don’t tell; write about how John touches Mary, looks into her eyes, how he feels when she touches him; instead of saying, “John loved Mary so much.”
Terminology
This is a hard one; the ‘correct’ terms for body parts can sound clinical, the more vulgar ones sound nasty and - well - vulgar, and will be an instant turn-off for many readers. I’d say you’re safest with the milder slang terms. It’s usually better to just use the word, or be a little vague if you want to be more romantic, than to make up elaborate and often bizarre ways of referring to sexual parts. Most of all, please don’t use ridiculous or cutesy names, avoid clichés (manhood, womanhood, comparing female genitalia to flowers and male to weapons, etc.), and a little of referring to things as 'throbbing' or 'pulsating' goes a very long way.
A lot depends on the intended impact of your story; if sex is the main theme, be straightforward and use the appropriate words. If romance is more important, don't get into a whole lot of physical detail, but concentrate on the emotions and sensations involved. It also depends on your audience, some people don't like explicit words, others don't like euphemisms and vagueness. You probably won't be able to please everyone.
Beyond Kink
Finally, let me make it clear that I’m not talking about scenes of rape, sex with children, sadism, bestiality, or anything of that nature. Stories dealing with these subjects may be valid and worth reading; but they are not sex scenes, should not be written that way, and should come with a warning telling the reader what to expect. I’ll repeat that, many readers do not want to see these things; include a warning.