Summarize:

Once you're exactly sure of where you want to go and when you want to go where, where you want to stay and how you want to get around, make your reservations. For flights, again, book around two months out. And don't wait till the last minute for your hotels either you don't want them to be booked or almost-booked (because then prices skyrocket). And anything else for that matter, too. Many attractions have ticket sales online where you can skip the lines and go right in. Sure, the idea of waiting in line right now doesn't sound so bad, but for three minutes of work right now you can not waste hours of your vacation standing in a line with strangers wishing past you would've had better sense. While you may not want to pay premium rates for something that might not happen, you should nonetheless have some protection in case you could not travel during the time your tickets are booked for. The average one week vacation will cost you in insurance needs approximately $75 dollars. This is not a lot of money considering the security it buys you. Only you know if you are one of these people that changes their mind often, or often does re-scheduling or if you are one of these people that will fly out in a hurricane, no matter what! Some countries require a visa to enter and exit the country. Does where you're going require one? If so, do this as soon as possible. If something is to come up and you don't have one, kiss your trip goodbye. Barring countries that take monetary bribes, they will tell you to turn around and get a flight back home if you don't have one. Keep your passport, travel documents, visas, and similar items in a safe pouch. You may want to make copies, too, and keep them in a safe place. It will make it so much easier to replace anything that you lost. For starters, notify a friend or family about your leaving. If possible, leave them a contact number or address. If anything goes wrong, you'll be able to hear about it. And if anything should go wrong on your end, they'll be able to take care of business back home. If applicable, put vacation notices on your e-mail, and remember to set your answering machine. Those messages will just have to wait until you get back.
Make your reservations for flights and accommodations. Consider travel insurance. If traveling internationally, make sure your documents are in order. Notify the right parties that you're leaving.