Many vacations who normally spend the summer roughing it have decided this year that they are past tents. Instead of hiting the hiking trail, they're hitting the deck.

"Houseboating is luxury camping at its best," says Ginny Ade, who has been writing about the outdoor scene for more than two decades. In recent years, however, she has mostly concentrated on the latest rage in camping houseboating. She has written a chapter on the subject in this years edition of the "Campground & Trailer Park Guide" (Rand NcNally, $6.95). It's the most comprehensive article on houseboat vacations we've run across.

"Renting a houseboat is rather expensive," she writes, "but not when you consider that everything you need is usually furnished, with the exception of food, gas and personal toiletries." She points out that rental cost for a houseboat is tough to pin down because of the many variables: the length of the season the boat is rentable; the length of time you'll be using it; and the length of the boat (from a compact 28 feet to a floating palace of more than 52 feet).

The cost will also depend on the time of the year and on whether the locale is a highly popular resort area or a less frequented spot. Very roughly, you can figure on spending from $150 for a weekend to $650 for a week. In addition, expect to lay out from $50 to $100 for a security deposit, which will be returned when you return the boat in good shape.

If you're planning to take a houseboat vacation this year, be sure to plan early because most rental firms require early reservations. You'll also have a better chance of getting the vacation dates and the houseboat of your choice.

Even though anyone who has a valid driver's license and puts down a deposit can legally take out a houseboat, Ginny Ade strongly recommends that novices take one of the many free boating classes sponsored by the Coast Guard Auxiliary, the Power Squadron or the Red Cross. To find out where classes are being held in your area, write to: National Director, U.S. Box 345, Montvale, N.J. 07645; Red Cross, 17th and D Sts. NW, Washington D.C. 20006.

If you can't get to a class, send for a copy of the Official Coast Guard Boating Guide, Supt. of Documents, U.S. Government Printing Office, Washington, D.C. 20402. The cost is nominal, and "it should be required reading for the would-be skipper of a houseboat."

There are two general types of houseboats, she says. The most common for rentals is the pontoon type. It's powered by outboard motors, and any enginer problems can usually be taken care of easily. The other type is the standard hull housboat. Though it can cruise at higher speeds, it's tougher for novices to handle. "The havoc first-time houseboat skippers can create if they make a mistake is awesome." However, she points out, with proper instruction and a little practice, almost everyone can handle either type of houseboat.

Even though you're an old hand, she says, insist that the rental agent of his representative take the boat out with you for a trial run. Different boats handle differently, she cautions, and it's a good idea to have a representative along when you check the vessel for livability. Check to see that the toilet, shower, refrigerator, water pump, holding tank, fuel and lights work properly. Also make sure that all needed equipment is aboard - boat hook, anchor, boarding ladder and life jackers. Also see if the windows have screens.

Most rental houseboats have large open cabins forward, a roomy interior cabin for all-weather entertaining and dining, and staterooms for sleeping in the rear. The galley will have a refrigerator, stove and pressure water system, and usually an open deck with a grill for outdoor barbecuing. The bathroom has a lavatory, toilet and shower.

Live-aboard gear usually supplied with your rental includes silverware, cooking utensils, dishes, linens, blankets towels and pillows, however, don't take these for granted. "If it's not spelled out in the brochure or contract, ask about it," Ginny Ade advises. She also suggests that if you have sleeping bags eliminate bedmaking, and they can double as sun-deck pads, which keeps them dried out. Bedding on a boat tends to become damp and clammy, particulary if it rains during the cruise."

Other things to bring from home include; groceries, matches, charcoal, rain gear, tennis shoes, portable radio, binoculars, work gloves, fishing tackle, sunglasses, camera and film, cards, books, flashlights, an ice chest to supplement the refrigerator, and a 50-foot extension cord for electrical hook-up at marinas. Also be sure to bring along a first-aid that should contain sunburn lotion, insect repellent and calamine lotion.

You can get information on rental houseboats from the Houseboat Association, Charelston, S.C. 29407. You can also get information from state tourist divisions or local chambers or local chambers commerce.