Erotica is a much maligned and undervalued writing skill.
Yes, you heard me; skill. Writing sex without making your reader cringe and squirm with embarrassment is hard (no pun intended), but there are three mistakes in particular which really strip the erotic from erotica.
The “love stick” *ahem* cock-up
Please, dear God, for the love of all you hold dear, drop the “quirky” genitalia nicknames and stick to the basics. You might giggle like a school-girl when you write the word cock, but trust me when I say that “Love Stick”, “Throbbing Rod”, “Man-Meat”, and (yes I have seen this one used) “Plunger” are one million times worse. Unless you’re writing satire, just stick to the common colloquialisms and leave the “Velvet Cavern” out of this, okay?
Twister, A.K.A “where did that body part come from??”
Keep track of your limbs, guys. Well, not your limbs, not unless you’re doing practical research, but the limbs of the fictional characters you’re pushing into debauchery. An arm reaching where an arm could not reach might not kill the scene entirely, but a curious reader will stop to re-read and figure out how that could possibly (impossibly) work, and that will leech out the tension you worked so hard to craft.
Waves and Seeing stars; the Cliche conundrum
Purple prose is a killer most of the time anyway, but as writing trends gravitate to lean, effective, and even gritty (I know, I know, trends should be made, not followed) it’s becoming more of a turn off for both readers and agents. Even the fluffiest of sex scenes can suffer under cliched metaphors, flowery description, and draw out, blow-by-blow (pun definitely intended) descriptions. If you can find it in the kind of romance novel that has a cowboy on the cover you might want to update your sexual vocabulary.