SUN AND SAND in a week-long spree. By the tens of thousands, America's college youth flock to Florida each year on Spring Break. In March and April, a carpet of young bodies toasts to a bronze on the beaches, surfside bars pour beer by the gallons to anyone 19 and older and the revelry is nonstop.

It's temporary escape from textbooks that's been going on so long that this yer's migrants can claim parents who had their fling 25 years ago at Florida's two most-famous Spring Break capitals on the Atlantic, Fort Lauderdale and Daytona Beach. The escapades may have seemed tamer back then, but the young crowds of the past sometimes got a little wild, too.

Now two former Yale students, Bruce Jacobsen and Rollin Riggs (Class of '82), have sampled today's scene and produced a 125-page guidebook, "The Rites of Spring" (Arbor House, $4.95), aimed at showing undergrads how to get in on the fun as cheaply as possible. And it is fun, they say, even for the multitudes who maintain propriety in the face of temptation.

The book also attempts to answer the big question: Where do you find the most action, Lauderdale or Daytona? Some city fathers aren't happy with their answer.

No doubt about it, things can get raucous down in Florida, say the authors as they point the way to booze and romance, for those who are looking for it (and many of the collegians seem to be). Lest concerned parents think otherwise, their offspring are not headed for a church outing. The book warns of such hazards as sunburn, drugs, drunk driving, strict police enforcement and unwanted pregnancy. (In other advice, Florida's landlords aren't likely to enjoy the tips on how to get away with crowding everybody into the same room to save hotel or motel costs.)

Still, a number of students go south for quiet relaxation -- as far from the "Animal House" fraternity party as they can get. The book directs them to some of the state's less-commercial (and more attractive) beach areas such as Captiva and Sanibel islands on the Gulf Coast and the 100-mile "Miracle Strip" of beach between Pensacola and Panama City on the Florida Panhandle.

Panama City is particularly popular with students from southern colleges, many of whom make it a regular weekend trip in the spring. Weekdays are quiet, but Saturdays and Sundays pop. A bonus is that prices are cheaper than in Fort Lauderdale and Daytona. A big minus is that, especially in March, these more northern resorts can turn chilly.

Jacobsen, 23, and Riggs, 22, who were editors on the Yale Daily News, came up with the idea for the book in December of their senior year while daydreaming about their next spring break. Harvard had set an example with its student travel guides. Over the holidays, their research revealed that an estimated 1.5 million collegians vacation in Florida, all potential customers. They wrote a book proposal, and it was accepted by a publisher almost immediately.

During their last college break, Riggs surveyed north Florida and Jacobsen took the south. Between final exams, they wrote the text, and turned in the completed book a month after they graduated. Subsequently, Jacobsen has become a reporter on the Miami Herald, where an upcoming assignment is to cover, naturally, the spring break. Riggs, a free-lance photographer in New Haven, is just completing a 50-campus promotion tour for the book.

As for the Fort Lauderdale vs. Daytona debate: Their candid advice is that Fort Lauderdale is wilder, but Daytona Beach, more genteelly decadent, shows collegians the best time. Some Fort Lauderdale citizens got angry over the description, says Jacobsen, who now lives in the neighborhood, but others felt a rowdy reputation might just draw even more paying customers.

It's an entertaining book, quickly read -- and, in line with the authors' emphasis on cost-cutting, easy to pass around the dorm if you want to save a few more bucks on a Florida fling.

SEVEN CENTURIES OF HISTORY: Richard the Lionhearted of England is probably the most famous of the Plantagenets, in large part from the Robin Hood tales of the good king with the bad brother, John. (In the movie, "The Lion in Winter," Katharine Hepburn played Richard's mother, Eleanor of Acquitaine.)

But the Plantagenet story covers almost 700 years of English and French history, reaching from 793, when the Scandinavian Vikings raided the northern English coast -- and set the scene for centuries of war and the rise of the Plantagenets -- to 1453, the date of the Battle of Castillon that ended English rule in the French lands of Acquitaine.

This summer a series of 27-day tours back to medieval Europe is planned to trace the heritage of the Plantagenets from the north of England to the south of France. It encompasses a span of time that saw the Norman Conquest at Hastings, the Hundred Years War and the emergence of Joan of Arc. One stop will be the Fontevrault Abbey, where Eleanor lived from 1194 to 1199, and where she, son Richard and her husband, Henry II of England, are buried.

Leading the tour is the Danishborn Peter Gravgaard, who has studied in Denmark, France, England and at Indiana and Yale universities and who has taught literature at the University of Minnesota and Odense University in Denmark. The cost is $3,945 per person, which includes roundtrip airfare between New York and London and all meals, hotels and other land arrangements. Departures are on the first day of the month, May through September.

For more information; The Plantagenet Tour, Elliott House, 1100 South Eighth St., Minneapolis, Minn. 55404 (612) 874-8109.

SOUTH CAROLINA SUMMER: Closer to home, and easier on the budget, is the tourist-conscious state of South Carolina. The Grand Strand, 55 miles "of uninterrupted family beach," as the tourist office says, is one of the state's most popular resort areas. To the west is "Up-country Carolina," the forests, lakes and streams of the Blue Ridge Mountains. There's the charm of historic Charleston, if that's your interest, or the Stock Car Hall of Fame in Darlington, home of the famed racing vehicles of Fireball Roberts and Richard Petty, among others.

A free 64-page, magazine-sized guide to the state's scenic, cultural and recreational attractions has just been published to help plan a vacation trip. It points out, for example, that on the Grand Strand, there are 12,000 camping sites and provides phone numbers for campgrounds along the beach and throughout the state.

To obtain a copy of the guide and a state map, write: South Carolina Division of Tourism, P.O. Box 71, Columbia, S.C. 29202. A calendar of events is available on request.

IN THE PATH OF MARTIN LUTHER: This year is the 500th anniversary of the birth of theologian Martin Luther, who led the Protestant Reformation in Germany, and dozens of escorted tours are being offered from May to November to places in East and West Germany where he lived and preached.

Among the historic sites: In East Germany, Eisleben, where Luther was born and died; Wartburg, where he translated the Bible from Latin into German; and Wittenberg, where he nailed his 95 Theses to the church door. In West Germany, the city of Worms, where Luther defended Protestantism, and Mainz, home of the Gutenberg Museum where the press is displayed that printed Luther's German Bible quickly.

Sample tours, available through Lufthansa German Airlines or a travel agent, include "Scenic Europe and the Heritage of Martin Luther" (15 days, $1,125 for room and two meals daily, American World Travel); "In the Path of Martin Luther (10 days, $715 for room and two meals daily plus lunches in East Germany, The Cortell Group); and "In Quest of Martin Luther" (10 days, $689 for room and two meals daily, Kuoni Travel). Airfare to Frankfurt is additional.

For a list of many other Luther tours offered by Ameican and West German travel firms, contact: German tours offered by American and West Third Ave., New York City, N.Y. 10017 (212) 308-3300. The tours can be booked through a travel agent.