Although it is convenient to travel without a carry-on bag, consider bringing one along. In your carry on, pack essential items like shampoo, a toothbrush, soap and a change of clothes (or two). This works well because you won't have to dig in your mountain of luggage to find your shampoo or toothbrush when you get to your destination. Also, in the event that you lose your luggage, you're not stuck without a change of clothing or toiletries.
It may seem like common sense, but always label your luggage with your name and address before departing. It's also a good idea to type out your contact information on a piece of paper and stick it inside the suitcase in case the luggage tag falls off during transport. You may also want to include the address of your destination in addition to your permanent address in case the suitcase is put on the wrong flight and it must be shipped to you.
Always allow yourself plenty of time to connect between flights. Avoid scheduling flights that come and go within an hour or two of one another. Try to have a layover of at least two hours in case the transfer airport is especially large or your first flight is delayed. If you're early, you can use the time to grab a bite to eat and relax a little bit.
Protect Your Body
Take vitamin C before getting on the plane. Take about 1,000 mg per day starting a week before and continue taking until you return from vacation. If you'd like, continue for a week or so afterward to make sure you keep your immune system in tip top shape. In addition, pack a small container of hand sanitizer and use before eating any meals or placing your hands near your mouth. If you're suffering from a head cold, take decongestants to avoid ear and sinus pain during take off and landing.
Those with Medicine
It is a good idea to carry all of your medication in your carry-on bag (especially if your checked luggage gets lost). If you suffer from a condition that could make you lose consciousness, such as epilepsy, have a card with emergency information readily available. This should include the name of a person to contact in case of an emergency, what company you receive health-care benefits with, the name and phone number of your doctor, as well as the names and doses of your medications.