Chances are, your readers are pretty familiar with sex and the mechanics involved. While you might have a not-so-typical sex act going on and want to explain it, beware of the dry textbook explanation.
Essentially, you want to explain the parts your readers may not know about. They already know arousal produces lubrication for women and increased blood flow makes a man’s penis hard. They don’t care. It’s all about feeling and imagining the magic of that arousal, not the biology of it. So don’t get technical. We’re not in high school with scientific diagrams.
Concentrate on the senses. Let the reader look through the heroine’s eyes as she sees her lover looming over her. Let her smell the masculine musk of her man, the scent of her own response as she goes wet with desire. Explore the taste of skin on her tongue. Hear through her ears as the moist sounds of lovemaking and the soft rhythmic patter of lower body meeting lower body fill the room. And of course the feel of the hero’s body against hers, of him entering her must be addressed. Give your readers a sensual feast to glut themselves on.
And since we’re talking sensual feasts, let’s have a look at a picnic scene from Alien Embrace. Here an innocent meal turns into a decadent opportunity for lustful consumption. By taking a non-sexual scenario into a wanton romp, I avoided falling into a nuts-and-bolts description of sex, letting dining on delicious food take the participants into the realm of a different buffet:
The sight of nellus delighted Amelia, but Flencik picked up a piece of grul. “Taste,” he invited, putting it to her lips.
She opened her mouth for his offering. A delicious spicy flavor filled her mouth and then—
“Hot! Hot!” she squealed, waving a frantic hand before her mouth.
All three men dove for the carafe of Plasian wine. Flencik grabbed it first. He tipped it into her mouth, quenching the fire set by the grul. It overflowed her lips, streaming down her chin to her throat and beneath her blouse.
“I made you mess,” he said in a soft voice, leaning close as he took the wine away. His breath wafted over her face. She closed her eyes against the nearness and felt the rough silk of his tongue lick the moisture from her chin. His mouth followed the stream until her collar blocked further progress. Then it traveled up the side of her neck.
The scene continues on with the three Kalquorians eating food off Amelia, turning her into a buffet until the need to sate carnal desires overcomes the group.
Amelia lay still, feeling every lick, nuzzle, nibble, and touch. The attention continued well after the food disappeared. A callused finger traced her spine. Strong hands kneaded her buttocks. A tongue slipped a wet path down the crevice to her anus. Another pair of hands slid beneath her to cup and squeeze her breasts. Lips kissed the nape of her neck, bringing gooseflesh.
“Don’t be afraid,” Rajhir whispered in her ear.
A strip of silky cloth was tied over her eyes, blindfolding her. Another bound her wrists behind her back. The bonds felt soft but tight. The sudden domination brought every sense alive. She lay still, wondering what they planned to do to her. Her juices flowed like a river between her thighs.
Now that I’ve told you not to turn your sex scene into a step-by-step instruction manual, I’m going to reverse myself just the smallest bit. In Alien Rule, Jessica was introduced to oral sex by Clajak. She had never performed it before, and with the well-endowed Kalquorian she required a little coaching. But even though he talked her through her first attempt at satisfying him this way, I still didn’t allow it to turn into a sex manual. Instead, I kept those instructions to the minimum while concentrating on Jessica’s reactions.
“Kneel before me,” he said, taking her by the upper arms. She obeyed, her sex flowing anew at the thought of taking him in her mouth, of tasting his alien flesh. She took a deep breath, letting his cinnamon scent flood her senses.
“I’ve never done this,” she whispered, her gaze locked on the two bullet-shaped organs.
“I will be delighted to teach you.”
He put one hand on the back of her head while grasping the larger of his members with the other. He ran the tip of the smooth-skinned cock over her lips, wetting them with his lubricant. She licked the fluid, tasting the sweet spice of him.
“Kiss it as you would my lips,” he said, and Jessica did, her mouth slightly parted, her tongue flicking out to tease. He was warm against her mouth, and she kissed his cock again, then again, becoming more passionate. Her hands gripped Clajak’s buttocks, squeezing the rock hard flesh as she slid her mouth over the tip of him, wrapping her tongue around his sex.
Sounding strained, Clajak’s honeyed voice commanded, “Now use your hand on it while you kiss the other one, my sweet.”
Jessica wrapped her hand around the larger penis. “Firmly,” the prince coached. “Yes, stroke me just like that. Now your mouth.”
Jessica tilted her head to one side to get to the smaller penis beneath her working hand. It had no opening for ejaculation; it had evolved for pleasurable purposes only. Remembering how Clajak’s finger had felt inside her anus made her shiver with anticipation.
She kissed and licked, delighting in Clajak’s sweet-spicy flavor. At his urging, she alternated between the two organs, both of her hands working his hard flesh. The veins running the lengths beneath each penis throbbed against her palms.
The insides of her thighs were slick with her flowing juices when Clajak pulled away. He looked down at her, his chest heaving with quick breath. He put his hands on either side of her head, pulling it back with his fingers tangled in her hair.
“Lean forward.” His voice was breathy, but still filled with command. She did as he directed. “Now I will fuck your sweet mouth,” he whispered. His predatory expression lent danger to his face. His fangs reappeared, giving Jessica an erotic fear-tinged thrill. “You feel how when your head is tilted like this, that your mouth and throat are in a straight line?”
“Yes.” Her voice was a bare whisper.
“It will help you to keep from choking. Keep your throat relaxed, breath only when I pull out, and you will be fine.”
He stepped close and bent over her, angling his larger penis. Jessica opened her mouth wide for him. His cock slid over her tongue, the vein throbbing. He slid in further, past the back of her mouth and into her throat. She stopped breathing, forcing herself to relax against the gag reflex. Clajak’s smaller penis ran down the outside of her throat, leaving a wet trail in its path. He continued to fill her with himself until he reached the end.
He pulled back until just the tip remained in her mouth. Jessica took a breath, then Clajak filled her mouth and throat again.
Listening to her lover’s breathing come faster, she filled with a sense of pride. The prince was finding pleasure with her, as inexperienced as she was. While she had always thought of herself as a strong, independent woman, she found it exciting to serve him. Hearing him command her to satisfy his flesh made her eager to do so.
After a few minutes of working her mouth slowly, the Kalquorian said, “Now a bit more energy, my sweet.”
His pace quickened, and Jessica fought to adjust to the new rhythm. He pounded himself into her throat, emitting growls as he took what he wanted. Jessica’s hands left his thighs to bury themselves in her own wetness, pleasuring her sex as the Kalquorian pleasured her mouth. The heat in her womb grew, sparking into an inferno. She plunged one finger, then two, then three into herself, matching Clajak’s pace. Her sex shuddered with the coming orgasm, spasming around her working fingers. Clajak’s gasps grew in volume, telling her he was closing in on his own pleasure, readying to pour his seed down her throat. Her desire grew brighter, brighter, almost there...
Clajak disengaged, pulling free of her clinging mouth. He bent over and yanked her hands from her sex. She cried out and struggled against him, desperate to claim completion for herself. He held her wrists easily, his lips curled in a cruel smile as he denied her the orgasm she’d come so close to having.
Make your own sex scenes a decadent feast to keep your readers enthralled. They know how the parts work. Show them how good it feels when the parts work well.