Susan Foster recalls checking into a chichi Hong Kong hotel and spotting a group of American tourists in the lobby dragging "enough luggage for three armies." Yet for the duration of their trip, Foster says, the tourists appeared in the same outfits.

"If they were wearing the same grubby stuff every day, I wondered what was in those suitcases," says Foster, author of the book "Smart Packing for Today's Traveler." "Obviously they didn't pack appropriately."

Foster should know. She has packed and unpacked some 4,000 times over three decades, she said, traveling first as a book publisher and later as a companion to her globe-trotting husband, who worked in international trade.

Some people heading out of town don't give much thought to packing, thinking it's something to do the night before a trip by dumping half their closets into flimsy bags.

Need encouragement to pack less? Consider that in August, when the Transportation Security Administration changed the rules about carrying on liquids, the number of pieces of checked luggage jumped 20 percent -- and the number of lost bags increased 33 percent compared with August 2005, according to a report last month by the Department of Transportation.

"The beauty of travel is that you are on vacation from all the material complexities of life," says TV travel host and guidebook writer Rick Steves, who lives out of one suitcase for more than 120 days a year. And he means one suitcase, and he always leaves room for small souvenirs.

Based on the advice of like-minded packing experts and guided by dozens of books and Web sites, we've assembled a five-step plan for packing wisely, with tips on how to accomplish each step.

1.PLAN AHEAD.Start thinking about what you're planning to pack at the same time you buy your plane tickets, book the cruise or confirm the availability of your aunt's resort condo in the mountains.

· Write down everything you think you'll need for a trip. Don't just make a mental list -- get it on paper. It'll serve as a good checklist, and if you're suddenly pressed for time, you'll have something to jog your memory.

· Before you start assembling items, check the Transportation Security Administration Web site (http://www.tsa.gov) to see what is and isn't permitted in checked luggage and carry-on bags.

· Think about what you're going to wear from the start. Would revealing clothing such as a bikini or deep-plunging neckline create an international incident? If you're planning a Christmas trip to Aruba now, do you need to buy any warm-climate clothes? Is your cruise strictly casual, or will you need to pack formal wear?

· Never pack the night before or day of a trip. Do it at least a day (preferably two days) ahead. Even if you don't stuff all the contents into your luggage, at least have the items stacked and organized. Once packed, if you must dip back into your bag at the eleventh hour, do it only to weed out items you won't need.

· If you take an annual ski or beach trip, you generally bring the same items each time. List those items on an index card and consult it before each trip, suggests Marla Cilley, a professional organizer known online as the FlyLady (http://www.flylady.net). When you return from the trip, edit the list.

2. PREP YOUR LUGGAGE.If your bag doesn't arrive in one piece, your vacation may fall apart, too. Take extra precautions, both inside and out, to ensure that you both arrive in good condition. (For the latest trends in luggage, see Page P9.)

· Don't pack so much that your suitcase looks like a marshmallow or can't close without the aid of a strap or bungee cord. If a security inspector cannot close it properly, you risk losing possessions.

· Most pieces of luggage have two zippers on one track. When closing a bag, pull the zippers all the way around the bag to the bottom; don't leave them at the top of the bag, where they could snag on something, Steves says.

· Use neon-colored duct tape, securely tied colorful yarn or ribbons or an oversize, colorful luggage tag to make nondescript bags (read: basic black) stand out on the luggage carousel. Or dare to be different and opt for a brightly colored bag.

· Take off removable straps. If they can't be removed, tuck them into pockets or secure them to the side of the bag with duct tape.

· Be sure your name, address and telephone number are on the bag, both on a luggage tag and on a card tucked inside the luggage. Include contact information at your destination as well.

· If you want to lock your bag, use a TSA-approved lock. TSA locks can be opened by security inspectors by using special tools provided by the lock makers. If you don't use an approved one, screeners may deliberately break your lock to search your bag. Of course, they may do this anyway with TSA-approved locks, but at least you'll decrease the odds.

3. PICK YOUR WARDROBE CAREFULLY."A lot of people have angst over this, because they don't think about it in a constructive way. They just stress over it," Foster said.

· Pick mix-and-match separates in neutral colors, such as black, navy and beige, and plan to wear each item more than once. You can dress an outfit up with an easy-to-pack scarf, belt, tie or jewelry (preferably non-valuable, non-sentimental pieces).

· Opt for wrinkle-free fabrics, such as microfiber, nylon or a cotton/polyester blend.

· Avoid bringing thick sweaters or fleeces by packing thin layers. Judith Gilford, author of "The Packing Book," suggests merino wool; it's thin, appropriate for most cool and warm climates and reshapes itself after wrinkling.

· Don't bring three pairs of jeans or three black sweaters when one good one will suffice.

· If you must bring bulky items -- including heavy shoes, fluffy fleeces, ski sweaters or winter coats -- wear them on the plane instead of packing them.

· Always pack a few quick-drying items that could be hand-washed in a jiffy, including T-shirts, underwear and lightweight trousers.

4. KEEP TOILETRIES TO A MINIMUM. Most travelers are surprised how many extra pounds a full array of beauty products can add to a bag.

· Bring travel-size items, not full-size ones. If you can't find a teensy version of what you need, check out Minimus (http://www.minimus.biz), which sells only travel-size products. Its inventory ranges from 21-cent Dial antibacterial soap and $1.29 miniature deodorant to packets of light ranch dressing for 66 cents.

· Pack items in leakproof resealable bags or clear toiletry bags, which will help you find items without having to unpack everything.

· Consult experts' packing lists for medicine suggestions, so that you don't end up bringing more than you'll need.

· If you're headed someplace where replacement toiletries won't be readily available, look for products that do double duty, such as shampoo that's also body wash or a sunscreen that's also a skin moisturizer.

5. PACK THOUGHTFULLY.The key here is packing every inch of usable space in a bag without overpacking. Experts battle over which packing method is best, but go with the one you're most comfortable with.

· Consider rolling as many of your clothes as possible. "When soldiers pack their stuff into duffels and need things to take up as little room as possible, they are taught to roll everything," explains Ramona Creel, a professional organizer in Clinton who runs the Web site OnlineOrganizing.com.

· An alternative to rolling is bundling all clothing items together into one tight, pillow-like mass that takes up the entire suitcase, Gilford suggests in her book. Lay all your clothing items across the entire width of the suitcase, and once all items are piled up, begin folding in the arms and legs.

· Stuff shoes with socks, rolled ties, jewelry, underwear or other small items. Make use of this seldom-considered space. And if they're dirty, shoes should be wrapped in shoe bags or plastic bags.

· Books are dead weight. Instead of packing a library's worth of guidebooks, photocopy the relevant pages or even rip them out of the book.

· Electronics (cameras, iPods), jewelry, prescription medication and important documents (passports, tickets) should always be carried on. Likewise, remember that security agents cannot see through chocolate or peanut butter with X-ray machines, and packing those items may provoke a security check.