Plan ahead. Start a list of what you want to bring and what you need to buy. Pack at least a few days in advance. Packing at the last minute will ensure that you forget something important and pack a bunch of stuff you will never need. Actually I start collecting things about a week in advance, adding and eliminating items as I go.
Packing Rule 2
Think neutral. I prefer black clothes for traveling. It is so easy to dress up and dress down with black. Black pants, jacket, and shoes go a long way. Three pair of shoes should do it (see list above). Use scarves and jewerly for add flair to your outfits. Just remember that places like Europe is a little dressier than the US. Skip the cut-offs, jogging outfits and running shoes, and you'll feel a lot more comfortable.
Packing Rule 3
Plastic bags are your friend. Pack underwear and knits in pastic bags that remove all the air. I just use regular zipper plastic bags and suck out the air with a straw until it gets very flat. Put your extra pairs of shoes in a plastic bag, and always put your travel toiletries case in a plastic bag in case something springs a leak.
Packing for Rule 4
I always take a little umbrella, just in case. And I no longer take a hair dryer. Practically every hotel has a hair dryer that is minimally effective (but good enough for me). I do carry a curling iron though, and for that I bought a dual voltage model. Many curling irons are dual voltage and my Revlon model was quite inexpensive. I do need a plug adapter though, since the outlets in Europe are quite different than in the US.
Packing Rule 5
Know what electrical equipment you need before you go. Europe is on 220 volts (instead of the US 110 volt service) That means if you plug your electrical appliance into a European outlet with an Adaptor without a Converter, the sparks will fly! You will need these for your hairdryer, hair curler, iron and any other electrical appliance brought from the US that heat-up and not dual voltage. You will need only a plug adaptor for a computer and camera charger.
A Converter converts the 220 volts to 110 volts so US appliances will work (without melting) An Adaptor works with the converter to adapt the US Plug to match the European outlet. To complicate matters further, not all European outlets are the same. An outlet in Great Britain is nothing like an outlet in France. For our first trip to Europe, I bought a converter and an adaptor kit that included adaptors for all Western European countries. I still use that kit.
Make photocopies of your passport, hotel membership cards and credit cards(with numbers to call if they get lost or stolen) and carry those in a zippered pocket in your suitcase as well as in your carry-on.
Packing Rule 7
Don't pack anything of great value in your checked luggage. Cameras and PDA's need to be in your carry-on.
Packing Rule 8
Don't bring heavy Guidebooks. Photo copy and bring only the pages of interest in a ziplock page.
Packing Rule 9
Pack light. Take only as much luggage as you can manage on your own YOURSELF. If you are taking trains, you will need to put them on and off the trains yourself. If you are staying in a 3-star hotel and even many4-star hotels, the rooms are quite small by American standards and there is very little space for extra luggage and have stairs after the elevator lift. I repeat, pack light.
Packing Rule 10
Check the TSA site to review the rules on what you can carry aboard. (It keeps changing) And when they say that your carry-on liquids need to be in a quart sized zip-lock bag, they mean a quart sized zip-lock bag. When they say bottles must have three ounce or less, don't push it. They confiscate tons (literally) of stuff every day. And pack some extra underwear in your carry-on... just in case they lose your luggage or buy it when you arrive.