Prepare your lists of destinations, and create a detailed itinerary if possible. Make copies of the itinerary. You will need to give it to some important people, such as neighbors watching your home, and family. Then research your destinations to find out what the weather is like, what customs you should be aware of and what languages are spoken there.
Start learning the foreign languages. At least learn some basic phrases that will help you get around if you are lost, in trouble or need something urgently. Also learn common responses so you can understand what the locals tell you when you ask the question. It may sound silly but a lot of people forget about learning the other side of things. Get some tapes or CDs to listen to in the car or at work so you start picking it up. Also purchase a pocket-size dictionary for each language so you can look things up and try to pronounce them if necessary.
Apply for a passport or get yours renewed if need be. Passports can take awhile to obtain, so make sure you do this several weeks (if not months) ahead of time. If you already have a passport, just check to make sure it's still current. You would hate to get ready to go somewhere and realize you need to have it renewed.
Get all your necessary shots and vaccinations. Foreign lands have foreign diseases, and you need to protect yourself. Look up what vaccinations are recommended and which are required for the places you are traveling to. If you have trouble locating this information, call your doctor and ask him to look for you. Get these at least a week before you plan on leaving in case there are any reactions to the vaccinations. Also, while you are at your doctor's office, get any medications refilled that you might need if you plan on having a long trip. You may not be able to refill medications at your destination. It's best to take more than you need so you have extra in case you stay longer than planned.
Get some foreign currency and traveler's check. You may be able to exchange them in the country for a better exchange rate, but get some ahead of time as well. You don't want to be stranded at an airport or boat port because you can't pay for a taxi fare. Plan ahead. Also, keep some of your money with you in your carry-on luggage and some in a separate location. If you lost one piece, you would still have some money to get by on. Have fun and happy traveling!