1. In-Stateroom Noise Can Be A Problem
Stateroom walls are not very thick and noise can sometimes easily carry into surrounding staterooms. Try to talk in a normal, but low voice. Also, some cruisers will turn on the TV and have it set on a loud volume. Try not to do this, especially at night. A loud TV can be easily heard and disturb someone that is trying to sleep.
Always remember, people can (and have) called security on their fellow cruisers for being too loud at night. Security will often go to the stateroom making the noise to tell the offenders to be quiet. Failure to comply the first time will usually just get the people a verbal reprimand, but continuous noise complaints could result in extreme consequences like being kicked off the ship in the next port of call or banishment.
2. Don't Steal From Your Stateroom Stewards Cart
Your stateroom steward's cart is usually a cart they push around that contains clean linens and things that need to be distributed to staterooms. Do not take things from their cart as this can make their job harder. If you need something, please ask your stateroom steward.
I used to be guilty of violating this one. Several years ago, when Carnival had chocolate mints delivered by stewards during nightly turndown service, the stateroom steward carts would have bowls of chocolate mints. As I passed by a steward's basket in the stateroom hallway, I would reach into the basket and take one (or more).
3. Dirty Dishes
I completely understand there are times when people need to get rid of dirty dishes that were from a previous room service order or brought back from the buffet. Typically, cruisers will deposit their dirty dishes in the stateroom hallways. I recommend putting your dirty dishes directly outside your stateroom if you choose to put your dirty stuff outside. Do not put them outside someone else's door or in front of a fire wall. Personally, I get slightly annoyed when someone leaves their half eaten room service order outside by my door.
4. Storing Your Suitcases & Bags When Cruising With Others
This can become an issue, especially if you are sharing a stateroom with friends. Due to stateroom space being limited, try to push suitcases under the beds. This may not be possible on all ships because of the amount of space available under the beds. If you cannot fit your suitcases under the beds, after unpacking, devote one corner to the empty suitcases for the entire cruise.
Try to keep your stateroom companions happy by limiting the amount of baggage you bring to begin with. Having less stuff to store should make everyone staying with you in your stateroom a little happier.