Cruise passengers often make mistakes before they board their ships.

Not buying a drink package in advance on Royal Caribbean and Carnival will cost you since pricing on board is higher. The same is usually true for internet packages and specialty dining.

Related: Royal Caribbean makes pricey Deluxe Beverage-Package change

If you don’t make reservations for excursions, you run the risk of them selling out. The same can be true for on-board experiences that can be booked before you board. Which things can be booked vary not just by cruise line but also by ship.

Royal Caribbean’s Oasis-Class ships allow you to book theater, Aquatheater, ice-rink and comedy shows before you sail. If you don’t prebook, you will likely still get in but you’re also likely to waste time standing in line. 

At the same time, not all cruise-ship mistakes happen before you sail. Some occur during your cruise, and the one I see most often is costly. 

Want the latest cruise news and deals? Sign up for the Come Cruise With Me newsletter.

Cruise-ship casinos attract people who might not gamble on land.

Image source: Daniel Kline/TheStreet

Avoid this costly cruise ship casino mistake 

Every casino, on land and at sea, tracks gamblers’ play by one of two methods. At some casinos, you must insert a player’s card while you’re playing. In others, you tap your card and it logs you in.

Royal Caribbean and Celebrity have ships that use both methods. But if you don’t insert your card or tap yourself in, the casino won’t know you played. 

This seems like a small detail, but not being properly logged into your machine (or, at table games, not handing the dealer or casino worker your card) will cost you dearly.

Cruise-line casinos offer lower odds than land-based casinos. Slot machines offer a payback in the high 80%s, while land-based casinos hover around the low 90%s. Broadly, that means that a cruise line’s slot players lose more money.

The same is true in video poker, where the payback tables are less favorable and the table games generally have more casino-friendly rules. 

Cruise-ship casinos, however, may be a harder place to win, but they pay passengers back in other ways — as long as they remember to tap or insert their card.

Both Royal Caribbean and Celebrity Cruises make regular announcements reminding people to log in to register for and record their play. Countless passengers don’t — including some who appear to be fairly heavy gamblers — and they’re costing themselves big money by not doing so.

Sign up for the Come Cruise With Me newsletter to save money on your next (or your first) cruise.

How do Royal Caribbean and Celebrity reward casino players?    

Slot players who remember to tap or insert their cards earn one point for every $5 they put through the machines. It does not matter if you win or lose; it’s all about how much money you cycle through.

Video poker players earn one point for every $10 put through a machine, while table players earn points but at a less specific scale. In general, the best path to free stuff is playing slot machines, since table games earn fewer points per dollar played.

Points bring value in three different ways.

Free play: The rates vary, but each point you earn can be cashed in for free play at the end of your cruise.  Casino status: The programs vary between Royal Caribbean and Celebrity, but both cruise lines have an annual casino loyalty program. On Royal Caribbean, if you earn 2,500 points across the casino year (April 1-March 31) you become Prime and earn free drinks in the casino (even when you’re not playing) and a free cruise for two on any sailing 7 days or under that’s not on an exclusion list.Cruise discounts and free cruises: The rewards tables can vary, but on my current Utopia of the Seas sailing, 1,200 earned casino points get you a free cruise from a fairly limited list. If you cash in 1,500 points, you get a longer list (and there are better offers at higher totals). Discount coupons for dollars off your cruise kick in at 400 points.

ALSO READ: Top travel agents share how to get the best price on your cruise

In addition, both cruise lines send people email offers, and sometimes you might get a discount or even a free cruise without hitting any specific level. 

But not tapping or inserting your card in the casino literally costs you money in rewards and chances at discounts and free cruises.

Related: Get the best cruise tips, deals, and news on the ships from our expert cruiser