Packing for a trip, whether it's a weekend getaway or a three week cruise can be a stressful undertaking. It is easy to forget an essential item; and it always seems like there is never enough room in your luggage for everything you want to take.

If you are traveling by air, you are generally allowed two checked pieces of luggage per person and one carry on bag. The carry on bag should be able to fit comfortably under the seat in front of you or in the overhead bin. The restriction on liquids is still in effect. All liquids, creams and lotions must be in containers of three ounces or less and contained in a quart size Ziploc bag.

Most experienced travelers understand the importance of carrying important items in their carry on bag, rather than their checked bag, especially if an airline has lost their luggage before. Your passport, tickets and any travel documents should be in your carry on bag, along with any vital medication, spare glasses or contact lens and prescriptions. A basic change of clothing is also a good idea.

Virtually all airline tickets today are electronic, although if you do have a paper ticket you should carry a copy of it in case you lose it. It is a good idea to make photocopies of your passport (the inside page with your information on) as well as any other travel documents. Keep these copies in a separate place. And you should also carry with you a list of important phone numbers to call in case your purse or wallet containing passport, tickets or credit cards are lost or stolen.

Many experienced travelers only take a carry on bag, regardless of the length of their trip. Traveling with just a carry on bag eliminates the often long wait at the baggage carousel, and, of course, the airline cannot lose your luggage.

One method of packing lightly is to put everything you intend to take out on the floor or bed in front of you, then consider each item individually and ask yourself "How often will I use it?" and "Do I really need it?" If you will only use the item rarely, you should consider leaving it at home. When packing your suitcase, place larger and heavier items on the bottom, and smaller items on the top.

Many items can be purchased inexpensively and easily, rather than having to take them with you. Simple toiletries, film for your camera and beach clothing can easily be found just about anywhere. Items that you feel you should take, but may not need, such as waterproof clothing and first aid items can be purchased when you arrive at your destination, if necessary. Most hotels now carry a selection of basic toiletries for guests who may have forgotten something.

Consider packing clothes that can easily be mixed and matched and will complement each other, rather than taking several different outfits. For example, a pair of neutral trousers will match several different sweaters or shirts. Most travelers can get by with just two pairs of shoes, a sturdy but comfortable pair for walking and sightseeing and a more stylish pair for wearing with dress clothes.

Shirts, suits and pants that do not crease easily or can be drip dried are also useful items to bring along. Most people find that a couple of changes of socks and underwear are usually adequate. Take along a plastic or mesh bag with you so that you can easily keep clean and dirty clothes separate. Many travelers have learned to wash small items of clothing in a hotel sink or bath.

Of course, the best way to ensure that you have everything is to make a checklist of what you are taking, and check the items off as you pack them. Some seasoned travelers start packing a few days beforehand to minimize the chance of forgetting anything important. If you are taking an item which can only be packed at the last minute, a note on your suitcase or on the front door can help you not to forget it.

In general, the most important items you will need to pack are going to be tickets and any travel documents, foreign currency and credit cards, camera and spare film, toiletries and medication. Some other things you may consider to be essential are spare batteries for various devices, an adaptor for plugging in appliances overseas, a book reading light, a wristwatch with an alarm and earplugs.

And if you have some spare room in your bag, don't forget your address book and a traveler's journal.