When cruise holidays go wrong, you have to admit -- sometimes it's your fault. Sure, Mother Nature can rain out your New Zealand cruise or a poorly timed cold can leave you in bed on a port day. But often, it's your mistake that gets you in trouble. Perhaps you didn't prepare for your trip as best you could, or maybe you said yes when you should have said no.

We hate to see anyone's sailing turn sour. We've identified 12 bad decisions that could ruin your cruise to alert you to potential pitfalls. When faced with these situations, we hope you make the right choices, so you can have the best cruise possible.

1. You don't read the fine print.

Heard the one about the blogger who was denied boarding because she was too many weeks pregnant? She didn't read the fine print in her cruise contract. There's all sorts of important information in there about instances where a cruise line can deny you boarding or kick you off the ship, when the line is within its rights to change your itinerary, what your responsibility is to obtain necessary travel documents and what the fees for cancelling are. Miss something important, and your cruise could be ruined before it begins.

What else can get you booted off a ship? More than you might think.

2. You pick the wrong season.

Cruise to Alaska early in May, and you'll find the salmon are not yet running and snow is still blocking hiking trails. Cruise to the Caribbean during spring break and your planned peaceful retreat might be overrun with tipsy revellers. Sail Hawaii in the summer, and you'll be out of luck for whale watching. Pay attention to seasonality if you have specific goals for your vacation; otherwise, you will be disappointed.

Discover the best time to cruise major cruise regions.

3. You choose the wrong travel companions.

Your travel party can make or break your cruise. If your mother-in-law is nagging you all week, kids are getting in the way of your R&R or that new friend isn't interested in the same activities as you, you won't enjoy the cruise as much as with more compatible cabinmates. Choose wisely -- or at least have realistic expectations before you set sail.

You'll have better results if your follow our etiquette tips for sharing a cabin.

4. You pack (or don't have) your travel documents.

Show up at the terminal without the necessary documents (passport, birth certificate, mandatory visas) and you will never make it onto the gangway. It's not only your responsibility to obtain the correct docs, but to carry them with you during boarding. Packing them in your luggage and handing your suitcases to a porter could end with no cruise for you.

While you're at it, you should also avoid these packing mistakes.

5. You skip the muster drill.

The muster drill is a mandatory safety briefing that takes place on the first day of every cruise. We know it's annoying, interrupts your first-day fun and isn't anything avid cruisers haven't heard before. But skip it and you will be found out -- and possibly kicked off.

Best to follow these do's and don'ts for embarkation day.

6. You climb on your balcony railing.

Horsing around 10 decks above sea level is a recipe for disaster. While cruise ship balcony railings comply with industry safety standards, your behaviour might not. Hoist yourself up to sit on your balcony railing, try to climb from one veranda to the next or even climbing on the patio furniture can quickly lead to you plunging into the waves below.

Here are more things you should never do on your balcony.

7. You smoke in your cabin.

Fire is one of the biggest dangers on a cruise ship, and lines protect passengers by limiting areas where passengers can smoke (as well as prohibit the use of candles and electronic heating devices in cruise rooms). Smoking is forbidden in your room. If you choose to light up in your cabin, you run the risk of accidentally starting a fire, and if caught, you'll most likely be fined and might be booted off the ship at the next port of call.

You also should not do the following things in your cabin.

8. You forget the all-aboard time.

Your ship might be leaving port at 5 p.m., but that typically means you need to be back onboard by 4:30 p.m. Whether you lose track of time while enjoying daiquiris in port or you never noted the all-aboard time in the first place, if you show up late, the ship won't always wait. And if you race back to the ship in the nick of time, you will have made yourself a 'pier runner' and dozens of balcony dwellers will ridicule you as you rush, breathless, toward the gangway.

Missing the ship is just one epic fail -- Cruise Critic members have engaged in many others.

9. You ignore your kids at the pool.

Face it -- unsupervised kids at the pool are annoying at best and a danger to themselves and others at worst. They take over hot tubs and splash sunbathers -- but they can also slip and hurt themselves or fall into pools with no lifeguards to rescue them. Don't let your family holiday turn tragic by putting your sunbathing desires ahead of your little ones' safety.

We've seen other types of bad behavior at cruise pools -- don't do those either.

10. You never put your phone in airline mode.

If your phone is downloading texts and accepting calls at sea, or in port if you don't have an international plan, you will be flabbergasted when you get your next bill. Roaming charges are outrageous on a cruise ship, so be sure to put your phone in airline mode or turn it off completely.

Can't disconnect? Read our tips for using your phone on a cruise ship.

11. You double tip in the spa.

Spa treatments on cruise ships don't come cheap. They are even more expensive when you accidentally double-tip. Some cruise lines automatically tack on a gratuity to your spa bill and leave a line for an extra tip. If you're not thinking straight in your blissed-out, post-massage state, you might enter an additional tip -- and be out more money than you planned.

You also should avoid these no-no's on your cruise ship spa day.

12. You pack all your clothes before disembarking.

It's a cliche -- but people do it again and again. If you plan to set your luggage outside on the last night of your cruise so it can be picked up and transferred to the terminal for you, do not pack the clothes you plan on wearing on debarkation day. You don't want to depart the ship shoeless, in your pyjamas. Leave a toothbrush and some deodorant out, as well.

These additional disembarkation mistakes can also turn your last cruise day sour.