I worked on cruises for 3 years. Here are 6 things I'd never do on board.

• I used to work on cruises. After many days at sea, there are things I'd never do on a cruise.
• I never wear my room key around my neck and try to avoid misnaming the ship.
• I never buy the drink package or pay for meal upgrades in the main dining room.

I've sailed around the world as a cruise-ship employee, and now I enjoy cruising as a passenger.

I love the salty sea air, waking up in a new country, and lazy days by the pool, but a week at sea could get more complicated this year with cruises predicted to be in high demand.

While fighting a little harder to secure a prime seat on the pool deck, you may as well also avoid some rookie mistakes.

Here are six things I'd never do on a cruise after working on them for three years.

Pay for upgrades in the main dining room

Typically, main dining room meals are included in the cost of a cruise. But in recent years, it's become common for cruise lines to charge guests extra if they want to upgrade to "supplementary" items like lobster or certain steaks.

I know $12 may not seem like much for a steak or lobster tail at dinner, but the cost of the cruise is supposed to include your food.

So, even though I enjoy lobster, I stick with the items without the upcharges.

Buy the drink package

I enjoy a piña colada by the pool or a Manhattan while listening to a jazz set after dinner. Even so, it doesn't make sense for me to pay in advance for 12 to 15 cocktails a day.

I've done the math on typical unlimited drink packages, and the cost simply isn't worth it for me.

This is especially true with a port-heavy itinerary. If I've gone ashore to explore all day, that means I'm not sidled up to the bar slurping down alcoholic slushies.

I prefer to buy as I go and take advantage of happy hour and other drink specials that are available on certain cruise lines. I also check the beverage policy in advance and bring on my own wine, if allowed.

Touch shared contact surfaces with my fingers

Fellow guests will never see me touching the elevator buttons with my fingertips. Knuckles and elbows do the trick.

Some cruise lines are better than others at wiping down commonly touched surfaces, but I don't take any chances. I avoid touching things others frequently touch, and I wash my hands frequently.

This strategy has worked for me, as I have never contracted norovirus, even when it was running rampant on a ship I was on. It's quite contagious and can linger on your fingertips even after using hand sanitizer. I'd definitely rather be safe than sorry.

Wear my room key around my neck

I never walk around the ship with my room key around my neck, and I especially never do this when on land.

There are two reasons for this. First, I see many passengers using the room keys dangling from their necks to flaunt their cruise loyalty status. It just looks pretentious.

The sophisticated cruisers with the highest status, with the most days at sea, never show off their fancy room keys.

That's because they know the more important reason — safety. In port, that room key bouncing off your chest looks like an invitation to be robbed. It screams, "I have money! Come and take it from me."

Misname the ship

English is a funny language that has its quirks. Naming conventions make that even more complicated.

Ships have proper names, and so do not require a definite article. For example, "Tomorrow I am embarking on Discovery Princess," or "I enjoyed scenic cruising on MS Westerdam."

If you want to look like a savvy sailor, learn to drop the "the!"

Plan my port-day itinerary so tight that I may not make it back to the ship on time

Oh, the recurring nightmares I've had about not making it back to the ship on time during a port day.

I've never missed a sail away, but I have cut it too close at times and have had to run down a pier or two. Just recently, as a passenger, my taxi driver got lost returning our group to the port at night.

When I realized how late we were going to be, I forked over $8 per minute to be connected with the ship. I pleaded with them to wait for us. It was a sprint through the port to get back on and we received quite a scolding from the first officer.

That time, we got lucky. In the future, I'll be giving myself more time than I think I need to make it back.