Every travel booking site is a little bit different, but generally the search process is the same. You type in your travel parameters (location, departure and return dates, number of travelers), and the site generates a list of options sorted by price, rating or whatever other designation you specify. The types of parameters you can request depend on the site. For example, most sites will let you look for only nonstop flights or refundable fares when you book airline tickets.
Most general travel booking sites let you buy airline tickets and make hotel and car reservations à la carte, or bundle them into complete travel packages. Buying a packaged vacation should save you money, but that's not always the case. You have to do a little bit of creative cost comparison and add up the individual prices to make sure you're actually getting a good deal.
As you're booking your vacation, some sites will give you more information than others. Expedia, Travelocity and sites like them will let you pick your exact hotel, flight and rental car company, but Hotwire and Priceline won't provide you with the final details until you've punched in your credit card number. Although they'll tell you the hotel's general location and star rating, you won't get the hotel's name or address until you enter your credit card information.
A few sites won't sell you the trips themselves, but they can help you narrow down the best deals on other travel booking sites. Kayak lets users put in their destination, and it instantly searches the rates on hundreds of other booking sites so you know which one will give you the best deal. Click on the option you want, and you'll be linked with the site where you can buy it. Fly.com and Momondo offer a similar service, but they compare airfares.
On the next page, you'll see how some travel booking sites let you name your own price, but this great deal comes with a catch.