It's Not Just Talking DirtybyBarnaby©
A few years back, I had to take one of those week-long business seminars where everyone pretends to be awake through day after day of training exercises that look great on paper but never seem to work when you return to the real world. As is the tradition, our first day began with an icebreaker. In this case, it was to list four true facts about yourself and one lie and then see who could guess the lie. In my case I wrote:
1-My 6 year old son is a genius
2-My first job was at McDonalds
3-I've never ridden a bicycle
4-My favorite film is Casablanca
5-I am an internationally known pornographer
Needless to say, all of the other attendees pounced on that last one as my lie but it was, in fact, true. (Number two was my lie. I never worked at McDonalds.) At that point I had been writing and publishing erotica on the Internet for more than a year with most of my fans seeming to be from New Zealand or the UK (based on emails and comments). After the truth came out, it was revealed that several others present had written erotica but never tried publishing it. One sixtyish, happily married woman said she's been writing it secretly for thirty years. Another young lady admitted recently having taken a stab at lesbian fiction.
Writing erotica, specialized as it may be as a genre, is still about writing. This means you will need to have at least a basic understanding of the rules of grammar. Those who know the rules can sometimes break them for effect. Those who break them regularly just come across as unprofessional. If you've not already attained this understanding, go buy a copy of THE ELEMENTS OF STYLE and come back later for the rest of this piece.
When it comes to your subject, you may think you know everything but you will still need to do some research. This does not, however, mean that your research has to come from your life. In fact--no offense--it will probably work out better if it doesn't. Erotica is one genre where the phrase "Write what you know" should not really apply. One thing to definitely avoid in your research is the pornographic film. While they maintain a valid place in erotic fantasy, these days they have become so stylized as to have little in common with reality. Reality, though, is something that written erotica needs to have at its heart in order to work.
Read. Not just erotica but all types of fiction. Pay attention to pacing and characterization. Both are governed by different rules in a short story than in a novel. A good working vocabulary is essential, also, but at the same time you never want to oversell it. Typing out line after line of moans and groans is not only not erotic but it becomes a sloppy and boring cheat to the reader. Erotic fiction can be simple or complex but rarely uses words too big for the average reader to recognize.
Don't forget that sex, by definition, is a sensual act and that we all have at least five senses...six depending on how metaphysical you want to get. Don't do them all each time but in order to approximate reality, at some point you will have to describe not just the physical and the visual but the sounds, smells and tastes of what your characters are going through also. Remember, too, that the biggest human sex organ is the brain. Much of the sexual tensions between your characters can and probably should come through when they are not being physically intimate in your story.
Dialogue. Don't just describe what's happening. Have your people talk. When you write dialogue, don't worry about being grammatically correct. Write the way people speak. Read it aloud and if it sounds wrong, change it. If you can't hear it yourself, have a friend read it aloud to you. Where it makes you cringe, fix it.
If you write in third person, stick with that throughout. The third person is the omniscient narrator who usually shows no emotional involvement but can see all of the characters at all times and describe their emotions. If you choose to write in first person, you open up the possibilities of characterization for your narrator but limit yourself to only his or her point of view. Another important thing is tense. Most stories are told in past tense. If you choose to do this, then every single aspect of it needs to continue to be in past tense. Present tense is grating for some but if you choose it, again, make sure to be consistent.
Talk to people. If you're a guy, talk to male friends beyond all the bragging and listen for the actual emotions that come through in everything from long married sex to no-strings attached one night stands. Talk to women friends, too. If they don't perceive you as threatening, you will be absolutely amazed at just how much they're willing to share with you. Use all of this information to make your characters come across as real. Even the most perverted fantasies become more arousing when they are grounded in reality.
Most of all, have fun! Writing erotica is a liberating exercise in creativity. It's hard to hold yourself back and expect any success. Avoid cliches, emphasize character, use proper grammar and realistic dialogue and you, too, can become a successful international pornographer!