It can seem easier to pin Jell-O to a wall than to find the best price on a cruise. But you can find deals, especially if you are flexible. All it takes is vigilance and a bit of research.

Wait until the last minute ...

Most cruise lines have cancellation policies allowing for some sort of refund up to 90 days before departure. That's why the biggest discounts usually appear in that window. "Cruise lines use a book-to-fill model, meaning they want to fill 100% of cabins for each voyage to maximize their profit," says Emerson Hankamer, CEO of Houston-based Vacations to Go. "Since they want to sell out the ship, they offer markdowns on any available cabins."

While you may get a great price, booking last-minute may limit your choice of cabin, as well as restaurant reservations and shore excursions. To find the latest deals, you can check the 90-Day Ticker at Vacations to Go or sign up for Cruise Critic's Price Alerts and receive notifications by e-mail when prices drop or increase on specific sailings, itineraries, destinations and cruise lines.

... or be an early bird.

If you know exactly which ship, cabin type and location, when you want to sail and the itinerary, you can often get a good deal by booking as soon as an itinerary is announced — typically 18 to 24 months in advance, according to Cruise Critic editor in chief Colleen McDaniel. While the cruise lines may not discount the cabin per se, they reward early bookers with add-on incentives such as free or discounted airfare, beverage packages, prepaid gratuities and onboard credits, which can save you hundreds of dollars. Early birds may also be rewarded with the chance to bid for stateroom upgrades.

Consider repositioning.

Ships don't stay in the same place year-round and must be repositioned for maximum service. The Mediterranean is not smooth sailing come winter, and Alaska's ports of call essentially shutter from October to early May. That means many ships may deploy to the Caribbean or look to ports in Southeast Asia in the winter. Cruise lines hate sailing empty, so a trip from Barcelona to Fort Lauderdale, Fla., or from Seattle to Miami is priced aggressively to sell.

During our interview, Hankamer found a 14-night transatlantic trip from Barcelona to Rio de Janeiro on the luxury brand Oceania Cruises for $1,899 per person and in recent years has seen cruise fares as low as $75 per night per passenger.

Repositioning cruises have trade-offs. On the plus side, you may experience some unique ports of call, transit the Panama Canal, or have more time for workshops and onboard lectures themed around topics such as cooking, world affairs or photography. In the minus column: Depending on the route, you may have numerous days at sea, cross large expanses of open, sometimes rough water and have to deal with the extra cost of an "open-jaw" airline ticket — where the origin and destination are not the same in both directions.

Look to shoulder seasons.

While cruise lines schedule Alaska sailings in May and September, they also know many passengers worry it will be too cold. Those willing to take a chance that the weather gods will look kindly upon them will probably find extra discounts. In fact, the savings may be as much as 75% off regular fares, plus value-added amenities.

The same holds true for sailing the Mediterranean in April, May and September. Plus, McDaniel says, anytime kids are in school is a good time to sail, because you will probably have a more adult experience and family-oriented cruise lines are more likely to have extra cabins they need to fill.

Be willing to take a risk.

One of the best times to find an affordable cruise is during hurricane season, from late May to late October in the Caribbean. "I often cruise during hurricane season and have never had a trip disrupted," McDaniel says. "The great thing about cruise ships is that they can change course and move away from storms. So worst case is you may see different ports than originally planned." She notes that while the odds are in your favor, you should buy travel insurance just in case.

Find an experienced travel agent.

A good one will take the time to understand your needs and match you to the right cruise. They may also have access to deals not widely publicized and will give you notice of sales or deals when they see a price drop.

Shop at Costco.

Members of this warehouse store reap big rewards. For instance, book through Costco and you may receive a shipboard credit. If you don't spend it all on board, let the cruise ship's reception desk know, and Costco will issue a refund to your credit card for the unused amount. Or, Costco may offer a rebate in the form of a Costco Cash Card received after your cruise is over. In addition, executive members earn an annual 2% reward on Costco Travel purchases, including cruises.

Look into every possible discount.

There are other options for obtaining a deal. Being loyal to a specific cruise line can net you some savings; repeat passengers typically get a small discount on a future cruise. McDaniel also reminds travelers they may able to use points or miles accrued through credit cards toward a cruise. Hankamer says you may also find discounts based on age (55-plus) or profession, such as first responder, military officer or teacher. Also home in on the base price of the cruise. Your price may bundle in a drink package, airfare or shore excursions. Often the cruise line will reduce the fare by subtracting the add-ons you don't plan to use.

McDaniel puts it best when she reminds cruisers, "You need to understand the difference between a good value versus a great deal. If the ship isn't a fit, then no matter how little you paid, it's not a deal. But if you are happy with the price you paid and have an experience that blows your mind, then that's the best deal of all."