Take clothing that is comfortable, machine washable and can be layered to adapt to changing temperatures. Choose items that resist wrinkling so they will look better when they come out of the suitcase.
Resist the urge to pack most of your wardrobe; instead, take clothing that can be worn several different ways and for several different purposes. If you're a tragic over-packer, do a dry run so you have room for all those must have souvenirs.
Pack a good pair of walking shoes, a pair of waterproof flip-flops or sandals and one pair of dress shoes if you're planning to live it up on a cruise ship or in swanky restaurants and nightclubs.
Consider taking a backpack and a money belt. You may also find it handy to carry a sturdy and comfortable day backpack around rather than your usual purse or handbag. Many men also prefer to carry secure pouches rather than stuff their wallet into their pants, especially when travelling to foreign countries.
Be sure to label each piece of luggage clearly with your name and contact information. You can also use a bright luggage tag, ribbon, or other distinctive item to make your bags easily identifiable. Luggage locks will deter thieves but might be cut off by authorities in the United States unless your lock is approved by the Transport Security Administration.