Five hundred romance novelists have packed up their throbbing hearts and returned to private sanctuaries (there are 44 of them in the state of Virginia alone) to grind out a little more fictive yearning.

For more than three days they packed the inadequate elevators of the Mayflower Hotel up and down, up and down, on their way to meet or find literary agents, to drink Cokes or whatnot, to share (as the current jargon has it) both their shaky techniques as writers and their hopes for fame.

Most authors of "romance novels" are women, and almost all their readers are.

There is nothing inherently wrong with women, it may be argued, but they appear to be different from men. Women do not buy pornography much, and men do not buy romance novels much. That is one difference, and a critical one for the general commercial success of the romance novel, which now accounts (the group reports) for a good half of all soft-cover book sales.

Some of the books have been profitable, and to the stranger new to the genre almost all are amazing. ("This was Christopher, no longer a memory, a dream, but with her in this tent . . .")

Here is the opening sentence of one that sold 3 million copies, entitled "The Flame and the Flower":

"Somewhere in the world, time no doubt whistled by on taut and widespread wings but here in the English countryside it plodded slowly, painfully, as if it trod the rutted road that stretched across the moors on blistered feet."

A fussy writer would in pity have given a foot powder to the poor blistered road and put it out of his mind as one of those things you flat can't help. But the author of the sentence, Kathleen E. Woodiwiss, of Princeton, Minn., did not blush, retch or otherwise attempt (after the commission of words to paper) to expiate the crime.

No, sir, she (and this is the gist of the romantic novel) went on.

The average writer of romance novels seeks acceptance just as she is, without one plea. And finds it, apparently. Not merely in the lofty heights of divine mercy but among 20 million readers in America alone, who absorb (if that is the word for their consumption of the books) 150 titles a month, or 1,800 a year. This year the readers who do not mind in the least the rutted road with blistered feet will spend about half a billion dollars on the books, and it is known that some readers spend $150 a month on them at their current price of $2 to $3 a copy.

If you feel the urge, you can find them in drugstores.

"Nobody ever said they were high art," said Rosemary Guiley, explaining to a reporter that romance writers do not really need to be locked up in the looney bin. The books are pure entertaiment, pure fantasy, she said.

And these books, she went on, are by no means easy to write. No well-known literary type, she said, has ever succeeded in writing one that sold well.

Possibly because no matter how depraved writers are, it is hard to force them to write endlessly about broad shoulders and rippling bellies.

"I have read romance novels for years," Guiley said, "among many other things. Two years ago I thought I'd try writing one myself. This is the way so many romance novelists begin their career. They have read them, liked them and want to try writing them. Romance novels are maybe the best way for an unpublished writer to break into the book market."

Guiley, a pretty, yellow-haired woman in her thirties, has a husband, Bruce Trachtenberg, a public relations man for Reader's Digest, and they live in a Dutch Colonial 52-year-old house in Port Chester, N.Y., with two dogs, both mongrels and both understood to be enchanting, suggesting a Doberman and a Norwegian elkhound, respectively.

Informed by his wife of her desire to write about blistered roads, as it were, the husband "did not think I had lost my mind at all, but like many men he did not understand women's interest in romance novels."

But she found precious little help in starting. It occurred to her there must be billions of women like herself, all on the verge of writing these books but not sure how to start or where to go.

Her goal is still to write some great books in this genre, but she has contented herself thus far with "Love Lines," an information-packed book on the various types of romance novels ("Contemporary Sweet" stories differ from "Contemporary Sensual" stories, as you might well guess), plus a gallery of some of the best-known romance writers, and sketches of the various publishers and what they are looking for.

And while she (and others one might talk with at the national meeting) modestly says the books do not pretend to be great literature, still you can see they like the books to be treated seriously as, well, works of art.

Guiley traces the descent of the romance novel from (Zeus, spare that thunderbolt) Jane Austen, and writers of similar excellence. She says there is "a difference in quality" between Austen and the blistered-road set, yes, but they are sisters under the skin.

The severest reader would have to admit delicious things, as well as amazing facts, in the Guiley guide-book to romance novels, such as a handy list of the greatest lovers of world history with synopses of their heats and fates. There is Tristan, there is Abelard, there is Prince Charles, the one that wed Shy Di.

In nature you sometimes see rock formations cleft with resultant slippage, with the stratum broken and lowered 50 feet, so no geologist is alarmed at the series Tristan, Abelard, Charles.

All wholesome humans, it is said, fancy themselves wayfarers in a planet of rutted roads, and all hope to extend the helping hand to others. As Spenser, not the Shy one, once said:

"Who travels by the weary wandering way

To come unto his wished home in haste,

And meets a flood, that doth his passage stay,

Is not great grace to help him overpast?

Or free his feet that in the mire stick fast?"

So Guiley was inspired to help the budding romance writer by giving the lowdown on all manner of publishing factors. Things that might not be instantly apparent to the beginning writer of romances (they are chiefly "middle-class, between 18 and 48; many live in small towns, few have professional backgrounds and many have plenty of kids so that writing anything at all is an achievement," Guiley says) were gathered in a chat with the author of "Love Lines:"

* Avoid adultery. Some romance novels now get the heroine married early on (in the old days they only got proposed to on the last page, but as Guiley said some readers didn't think that was soon enough), but then there are misunderstandings to keep the thing going for 60,000 words. These obstacles may be ingenious, but the novelist must remember that one of the difficulties of the romance-novel marriage is NOT adultery.

* Do not try breaking too much new ground. Incest and homosexuality, which may be dandy for the stage and the serious novel, are not going to sell books in the romance trade.

* Do not be as sweet as romance writers used to be. This is 1983. Women (in romance novels) are not ready to give up everything else just for Mr. Right. You may perfectly well write like an idiot, but try not to make the heroine sound like one.

* If you are a male writer of these novels (and there are some, though usually under female noms de plume) try not to wander off in your own fantasies. Women, for example, do not stand around admiring their breasts in a mirror (Guiley says), but the average male romance writer thinks they do. He projects his own enthusiasms. But women are quick to spot this kind of falsity, so stick to your last and stop drooling about bosoms which do not much interest lady readers.

* In sex scenes, which are increasingly expected in these books, keep your focus on the woman's interior, what she is thinking, how her heart is yearning, zub, zub, zub. We do not want an anatomy lecture (Guiley says) or a substitute for a peep-camera. Do not go on forever describing the woman--women readers know all about that--but be sure to describe the man, in somewhat general and idealized terms, how the light falls on his naked collar-bone, etc. Best to stay above the navel.

* If anybody sneers at your trade of romance novelist, remind him that "Jane Eyre" was called "unChristian trash" when it came out, and "Confessions" by Augustine was severely criticized, too, for that matter, along with the "Song of Songs."

* Most women have strong traditional values. Do not believe all you hear from the liberated camp. Women want husbands and children and don't forget it.

* Do not expect to make millions on the movie rights. Most successful romance novels have little action, which movies must have. It all goes on in the heroine's head in the best romance novels, what she thinks, how she feels.

* Do not try illustrations. They have been tried. Women don't like them. They know what Lance or Morgan or Butcharelli (try to give the guys sexy names, by the way) look like and they don't want to be contradicted by some dumb photographer or painter.

* Sex scenes must be in context. It won't work to have the heroine just take off for a weekend and accidentally run into Gomorrah. That is too close to porn and it won't sell in the romance market.

* Be mighty cautious with more than one man for the heroine. You may think that while they're about it, in their fantasies, they would like two or more. In the romance market, they like one hero to drool over.

* The woman always gets her man. This is the first and great commandment, and if you forget it, you might as well throw in the typewriter. But before you do (which might be the best thing, esthetically speaking) remember a publisher will pay you $3,000 to $10,000 in advance for a promising romance novel with royalties later amounting to another $10,000 to $20,000. So don't get too high-minded too soon.