Thanks to Violet Blue (who provides more context) I can link you to the Ten Commandments Of Smut, which is after being some excellent basic erotica-writing advice by M. Christian. Just one commandment for flavor:

II. Thou Shalt Not Own a Thesaurus

An exaggeration, of course (to get that vicious Roget off my case). The need to change a descriptive word after every sentence or paragraph is the clear sign of an amateur. Example: ‘cock’ in the first paragraph of the sex scene, becomes ‘rod’ in the second, ‘staff’ in the third, ‘pole’ in the forth … and you get my gist. The same goes for the silly need to be ‘polite’ in describing either a sex scene or various body parts. Unless you’re writing a Victorian homage (or pastiche), women don’t have a ‘sex’ between their legs, and a ‘member’ doesn’t live in a man’s trousers. If you can’t write ‘penis’, ‘clit’, ‘cock’, ‘cunt’, or the rest of the words you can’t say on television then find another job – or just write for television.