While I prefer sensual but nonsexual scenes (e.g. massage), I still read a lot of fics with varying degrees of erotic content, at all rating levels (Explicit and Mature are both quite enjoyable). This is a summary of my general preferences, so if you're writing a sex scene into a fic for me, you can make it something I enjoy.
The only pairing I really have no interest in is yuri/femslash.
While I still enjoy het, it's taken a back seat to slash and threesomes. My preferred threesomes are MMM or MMF.
I prefer sexual scenes to involve adults. I currently prefer Dubious Consent (DubCon) over Consensual, and I can also enjoy Non-Consensual (NonCon) -- more on that in a later section.
As the age of the characters goes down, my preference for consensuality goes up; putting younger characters in NonCon or strongly DubCon situations starts to feel more like fetish fuel, and makes me uncomfortable, reducing my ability to enjoy the scene. Which isn't to say that a good author can't pull it off, but bear that in mind.
If a character is in their late teens (16+) and portrayed as reasonably mature, I'm fine seeing them in a sexual context with an adult, if the setup is pleasantly consensual, angstily consensual, or mildly dubcon -- not coerced. Add in supernatural elements (vampire romance!) and it's even less of a worry.
A reminder: Hollywood is in California, where the Age of Consent is 18, so of course all our media uses that age as the baseline. But more than half of the United States is fine with 17, and several States are okay with a 16-year-old having sex with an adult. There's a charity that's trying to stamp out "child marriage" (which they define as anything under 18), but I see no problem acknowledging that a 16-year-old is a sexual being and that some of them are mature enough to contract marriage, with some level of oversight from family and/or the courts.
If a character is in their mid teens (14-15), the partner should be of similar age, or supernatural. Again, my delight in DubCon and NonCon doesn't much apply to younger characters, so stick to very lightly DubCon or fully Consensual -- no coercion.
I have little interest in sexualizing youngsters (roughly 13 or younger, or any minor portrayed as particularly childish or naive). However, I've come across a couple fics that used worldbuilding and/or circumstances to make the setup plausible, some where it's pleasant and others where it's deliberately fucked up. And in an AU where biology is more of a factor (e.g. Omegaverse), I'm okay with young characters getting into sexual situations as soon as they're biologically ready, even if they're not emotionally ready (because that sort of setup is one way to symbolically deal with the changes of puberty and induction into the adult world). I'm not after mere fetish fuel, but I'm not triggered or troubled by underage fics.
I prefer one character to be in charge of the other's experience, though I have no preferences for which character is in charge, and I also enjoy seeing them switch off (one encounter has Bob in charge; the other has Alice in charge). In threesomes, having two characters lavish attention on a third is fun, and having them switch off who's getting the primary attention is also fun.I prefer one character to be in charge of the other’s experience, though I have no preference for which, and I also enjoy seeing them switch off. So I guess that power exchange dynamics (Dom/sub) are a thing for me, even if not in a Dom/sub universe; equality in a “nobody’s in charge” way isn’t nearly as engaging. Since the pairs I most enjoy tend to be damaged in some way (e.g. Person of Interest’s Finch & Reese), I see a lot of a character being willing to give over everything and having the other character choose not to take 100%, but be careful with the gift given to him. This is highly appealing. I like the Dom/top encouraging the sub/bottom, like praising him for using a safe word, to ensure that the sub doesn’t hurt himself through being too willing to endure (or feeling like he deserves to be hurt or to not have pleasure). Checking in now and again, and being careful of boundaries. However, I find it less enjoyable when the Dom is unsure and puts the burden of making decisions back on the sub. Isn’t part of the pleasure of the sub being able to turn over everything to the Dom and receive pleasure/experience without having to decide what you want? Definitely appreciate a level of nonsexual touch along with the sex. Like cuddling afterwards, or massage. Showing that the relationship is more than just the sexual component.
These two AUs are my preferred worldbuilds right now, bringing up issues of gender stereotypes in a way that is more interesting and less on-the-nose. Dom/sub and Omegaverse I’m hooked on these worldbuilds, and love encountering them in new fandoms where I haven’t seen them before. It took me a while to appreciate them, but the variety of these worldbuilds just astounds me. I like struggle, and frustrated yearning that doesn’t resolve right away, so no “love at first sight” stuff -- the characters can be wary of each other, have misunderstandings, have good reasons not to just give in and let their biology match them up. And characters who are biologically mating pairs don’t need to devolve into sexual relationships, just like men and women can have relationships IRL that have nothing to do with sex. Biology I don’t mind female Alphas, but definitely prefer the landicae variant to any ladydicks. Landicae are the adaptation of the clitoris to act as an Alpha knot so as to satisfy an omega’s heat; basically, imagine a handful of thin tentacles that can bunch together and stiffen up into a knot the size of a baseball, providing intense physical pleasure for both the Alpha and the omega as it locks them together. I have no preference between male omegas having slits (vaginas) or cloacas (anus connects to uterus); same for if they’re mostly just fertile males or if they’re a mix of male and female traits. I also have no strong preference for MPreg or not MPreg; either’s fine. But if MPreg exists, then definitely not C-section deliveries; the omega cannot be an evolutionary adaptation to provide greater fertility to the human race if he can’t even deliver the babies without medical intervention. In Omegaverse, there is no rationale for males and females to be segregated in bathrooms or locker rooms. Having an omega room separate from the Alpha room makes sense, but not a male Alpha and female Alpha room or whatever. The point of segregation is to separate breeding partners. (Betas might still be separated, I suppose.)
Keep the mess reasonably under control; getting sperm everywhere is a turn-off, especially getting it on the face (tasting it is fine). I don’t like gross stuff; definitely no scat. I've read a couple fics that made watersports endearing, but the idea still mostly grosses me out.
I do, however, quite enjoy Omegaverse, and there’s a certain amount of mess that comes with the territory; that’s not such a big deal, especially as it’s mostly within the body instead of getting all over the sheets/clothes/bodies.
I prefer reading about penetration (anal sex or vaginal sex), to the extent that fics have felt incomplete without it. But blowjobs and playing around with one guy’s balls are also fun. Tender intercrural sex has been in a surprising number of enjoyable scenes I’ve read. Threesomes are best when two guys enter the same vagina (or same ass), and I find far less enjoyment from one vagina and one blowjob.
I have less interest in aggressive face-fucking or deep-throating; it throws me out of the moment.
That “tension and release” model is vital to good sex scenes. Ramp up the tension: yearning, teasing, foreplay, orgasm delay/denial. Bondage is great, especially struggling against bonds, or being forced to accept teasing or pleasure that you can’t do much about. Suspension is good.
These terms get used to make useful distinctions among fics, so let's try to suss out the distinctions here:
There's a distinction between NonCon and Rapefic, but people differ as to where the distinction lies. Let's look at a Venn Diagram:So, let’s make some distinctions: Rape vs. NonCon: Firstly, IRL these are both rape scenarios, but we’re talking fictional genre categories; I can enjoy either, but in completely different moods. Both of these involve an unwilling Victim (this should be obvious to the reader). Now, some see these tags as a distinction of whether it’s written erotically (NonCon) or not (Rapefic), but I think of it more in terms of the intentions of the Rapist character. The Rapist in a Rapefic is clearly a villain, and is using rape either to harm the victim (hurt or dominate them) or for the Rapist’s pleasure with no thought for the victim (self-centered or oblivious). These are generally not written in an erotic way, and the Rapist is generally not redeemable. I definitely want time spent on comfort/healing afterwards. By contrast, the Aggressor in a NonCon scenario is invested in the victim’s pleasure/welfare, and truly believes that the sex is going to be good for both parties. E.g. “Don’t do this -- please--” “Don’t worry, I’m not going to hurt you… you’ll like this, trust me.” The Aggressor runs right over the bounds of informed consent, for what he considers to be good reason (e.g. “I know you want it, you just won’t admit it to yourself”). Often played up erotically, a “protesting despite my own pleasure” or “forced into overwhelming pleasure” kinda way. The Aggressor is redeemable. The encounter may actually turn consensual (try to ignore the problematic connotations of this IRL), or maybe eventually the Aggressor will realize that the victim truly didn’t want it, and be overcome with guilt, at which point we get to explore how this fractured relationship can get healed through forgiveness and love. (Generally, the Aggressor’s backstory or “wounded” status (or non-human status) helps to “excuse” him overstepping bounds. I reiterate the “problematic connotations” line.) Variant: Victim strongly desires an aggressive partner and thus enjoys the encounter, but is unable or unwilling to express the desire openly, and must make a show of fighting/protesting it. NonCon vs. DubCon: While NonCon is definitely rape IRL, DubCon covers edge cases and “no one was at fault due to X” scenarios, so certain DubCon scenarios aren’t rape. However, most would probably still fall under that heading IRL. In both of these categories, the characters are invested in each other’s welfare -- they’re not trying to hurt or dominate the other. Where NonCon offers a clearly unwilling victim, DubCon offers cases where at least one character is unsure or ambivalent, or their ability to consent is compromised. It also covers scenarios where both participants are compromised. Generally, in DubCon, there’s an external force (Sex Pollen or similar, or getting drunk or drugged, etc.) that causes one character to want sex even though the other character ought to realize this and prevent them from having it. Sometimes it affects both characters. In other variants, the force is emotional (“I’m so upset about X that my emotional shields are down, screw it, let’s have sex”), or the characters kinda maybe sorta want sex but also kinda don’t (or have good reasons not to go there) and if they were fully in charge of themselves and being logical then they wouldn’t have sex, but of course they’re not fully in charge of themselves and/or they’re not being logical. In DubCon, the reader is clear as to the emotional state of the characters, and the fact that they do (to some degree) want this to happen. E.g. “I’ve always wanted a relationship with you, but I’m too afraid to screw up the friendship we have, only now I’m too drunk to keep pretending that I don’t want you.” Whether the character, if sober, would allow himself to take this step is beside the point -- one of the reasons this genre exists is to push stubborn clams past their hangups and into a relationship (here, we get to ignore the basic principle that a person can choose not to act on their own desires -- that wanting something is not the same as consenting to it). Please do see the section in the base document on Integrity Crisis, because that’s pretty much my favorite scenario when it comes to sex. So, with those categorical distinctions in mind: If it’s a sexual encounter between two heroic characters, I’m good with DubCon or NonCon. But if it’s a Rape encounter, it better involve a villain; I don’t care to see my favorite characters twisted to the point of becoming Rapists, at least in that vein.