GETTING READY: One of the most informative guides to read before you go is "The Companion Guide to the Loire," by Richard Wade (Collins, 333 pp., $7.95 paperback). While you are there, the Michelin green guide "Cha teaux of the Loire" (175 pp., $7.95 paperback) provides good, basic sightseeing details.

GETTING THERE: The heart of the Loire Valley cha teau country is about a two-hour drive southwest of Paris. Or travelers could take a train to Orle'ans or another Loire city and rent a car there.

TOURS: For guided bus tours or the names of outfitters offering hiking, bicycling and horseback-riding tours, contact a travel agent or the French Government Tourist Office, 610 Fifth Ave., New York, N.Y. 10020-2452, (212) 757-1125. Outdoors magazines and adventure guidebooks also provide listings of hiking, cycling and horseback tours.

Our 15-day hiking tour from Chambord to Angers is offered by Hiking International Ltd., 7 Blue Boar St., Oxford, OX1 4EN, England. The cost was $1,121 per person (double occupancy), which included all meals and comfortable rooms with bath in good hotels and inns. Luggage was transported by van from inn to inn.

WHAT IT COSTS: In the summer of 1985, a good double room with private bath ranged from about $20 to $40 a night in the cha teau towns and cities of the Loire, including a continental breakfast. During the busy tourist season, hotels fill fast, so reserve ahead or find a place early in the day. An excellent four- or five-course meal (not including wine) seldom costs more than $15 per person. Entrance fees are charged at all the cha teaux, ranging from $1 to about $2.50 per person.