Are you ready at a moment's notice to take advantage of a terrific cruise deal you see on an internet ad? You know the kind, such as: "Seven day discount sailing, hundreds of dollars off, all kinds of on-board freebees and free flight!" Attractive, but before you click in your reservation, there are details you must consider.

If the cruise ship is sailing out of U.S. territorial waters, you'll need a valid, up-to-date passport. Check at least once a year to make sure your passport is always ready to travel out of the country. When considering a last-minute trip, put together a travel package at home. For instance, keep a carry-on suitcase per person out on a couch. Pack the bags with three- or four-day supplies of casual clothing, meds, toiletries, packaged snacks and other needs. It’ll be easier to dash out of the house when you book a trip just hours away.

Hundreds of online travel agencies, including those who specialize in last-minute deals, are always ready to sell you a cruise. If you're thinking about signing up within the next couple of months, check with them several times a week, so you'll become familiar with the way the trips are offered and pricing.

There are certain times of the year when cruise prices are lowest, usually from September to March. Another consideration is if you're offered a theme cruise, make sure it’s for you. If you're 75, do you really want to sail with a thousand young rock fanatics and their ear-splitting onboard bands?

There are also the discounted repositioning cruises, where a ship that sails in northern waters in the summer makes a one-way trip to a southern port for winter schedules. It may require you must pay to fly one way, but the overall bargain in price may be attractive.

Another factor of last-minute cruises is destinations. Just because a cruise is a terrific bargain, do you really want to go to some third-world country where there has been recent violence, and protection ashore isn't assured? Also check cruise ship records of cleanliness, illness breakouts, onboard services, safety, customer satisfaction and other important considerations.

If you have a good relationship with a bricks'n'mortar travel agency, check with agents there from time to time. Let them know you'll consider last-minute cruises. Better than online agencies, they may be able to find last-minute passenger cancellations to offer you within days or hours of sailing.