Dear Soon-to-be-a-Winner:

I have uncovered an inside tipoff on one of the shrewdest racing coups ever attempted . . . This is the BIGGEST,the SAFEST,the MOST POSITIVELongshot Maneuver of the entire year . . . a special confidential winning maneuver arranged exclusively for Mike Warren followers only.

For a small $20 fee . . .

Sensible men who have their names on Mike Warren's mailing list and are periodically assaulted by promises of hot horses and sure-life systems might assume that their correspondent is a fraud, a phony, a hustler.

All these descriptions might have elements of truth in them, but Warren happens to be something more. He is a promotional genius. From the humble origins of his mail-order touting operation, he has built such a prosperous marketing business that he can now consider going strictly legit.

Warren was born into his profession, the son of an expert handicapper who sold tips on hot horses. He remembers admiringly. "My father would ask for $100 for (a tip on) a horse in days when $100 meant something, and he'd get it." As he grew up, Warren was encouraged to study the Racing Form the way most kids are prodded to study geometry. By the time he was 14 he was practically a regular at Jamaica Race Track.

In 1970 Warren bought a 3,000-name mailing list and went into business. He sent those 3000 names a letter promising the winner of the Kentucky Derby for a $15 fee. When his horse Dust Commander, scored at 15-to-1 odds, Warren was off and running.

He had certain advantages over rival tip and system peddlers, because he was a capable handicapper, having learned his lessons well as a schoolboy. Warren was also smart enough to understand the mentality of his customers, and brazen enough to capitalize on what he knew.

"They want instant riches," he said. "If I told people I'd get them a 10 percent, even a 50 percent, return on their money, it wouldn't go. I tried selling a system once with kind of a low-key approach; that didn't go. People want millions."

Warren would never write straight-forwardly that he had doped out a fit horse ready to be entered in an easy spot. He had to advertise that he had inside information about the betting coup of the year. He would never sell a book that shed light on some of the principles of handicapping. Instead, he would advertise a system promising the purchaser overnight success.

Some critics might term Warren's claims fraudulent. He would retort, "Everybody overstates their product. That's the American way. It's called marketing."

Warren's principal product - the horses he picked - was good enough that he developed an enthusiastic following. On a Saturday in New York, when the betting pools are enormous, he could put out the word on a legitimate 10-to-1 shot and make him 6 to 5.

And as he cultivated more customers, he developed a valuable mailing list that would serve as the springboard for his other operations.

He marketed other people's books on racing and gambling. He started a football tout service, which he considered a boom industry. He organized a successful junket to French and English race tracks. He is working on a train junket to the 1979 Kentucky Derby. He is even hustling a diet plan by mail.

With so many booming enterprises, Warren has become a rich man at the age of 36. And his ambitions have far transcended his original aim to be a great mail-order tout. "My goal," he said yesterday, "is to be another Sonny Werblin - a marketing genius."