Book last-minute. Airfare costs tend to skyrocket when reserving at the last minute. Not all aspects of travel work this way, though. Book cruises and tours late in the game and it’ll knock an easy 25% off your bill. No one wants to send out an empty ship or run an empty tour, so companies always scramble to fill spaces if they haven’t sold. The ideal time to get the best deal is a couple of weeks before your departure date. Conversely, booking ridiculously far in advance (such as a year or more) can also score a great deal. Go-today.com and lastminute.com tend to have terrific bargains.