Destination: Travel is easier in warm countries like Greece and Italy where you can eat outdoors and spills don't matter.
Luggage: Especially in summer, a child doesn't need more than he or she can carry in a knapsack.
Plane: Take food: peanut butter in a plastic jar, crackers or bread, small wrapped cheeses such as Laughing Cow, apples, raisins, cookies, and a bottle of water. Bring wipes and tissues, of course.
Health: Bring your pediatrician's phone number. In general, stick with bottled water.
Hotels: Stay in the town center so you can walk to the sights and return easily.
Museums: If there's something you absolutely must see -- the Mona Lisa, for example -- locate it immediately, because you may not be staying long.
Entertainment: Old-fashioned attractions -- such as ponies or sailboats in the Luxembourg Gardens in Paris and puppet shows on the Gianicolo Hill in Rome -- are charming and can be fun for both parents and children.
Expectations: Don't expect too much of the trip, yourself, or your child. Be prepared to shell out for treats and inexpensive trinkets. My son spotted a flyswatter in a hardware store window and was happy swatting things for hours.