the above posters did a good job discussing the extras. Most people don't realize how they will be paying extra for a bottle of water as they get off the ship in port or for the specialty coffees.
One small comment about tips. The porters often do not deserve much of a tip. If you are lucky, they will lift your luggage from your vehicle and onto their carrying machine. That's it. Since I always lift my own luggage out of my vehicle myself, it is that much less work. nevertheless, I ALWAYS tip these people about $4-$5 just to keep them from selecting my bag to open. You gotta figure that out of the hundreds of people that each porter comes into contact with each day, some people will be real jerks both verbally and stiffing them from a tip. THESE will be the people who get their luggage lost/misplaced/broken into.
As for room service, I distinctly remember on one of my cruises watching a video in the cabin about the ship and the zoomed in to show the passenger giving the room service person TWO one dollar bills, so I have to assume that $2 is the expected amount rather than the $1-$2 as suggested above.
To each his own about tipping, as I am aware that my $4 for 4 bags is below what some people tip.
Finally, if you go on any type of excursion, expect to get some pressure to tip the people who are giving the excursion. No matter that you and your spouse just spent $250 for the excursion, the cruise line takes a big part of that so the local who does all the work only gets a small portion of that and they will let you know and they ALWAYS make sure to tell you about the 7 kids that they have to put through school.
It seems that every person you encounter in the islands will be looking either to sell you a product, a service or begging for free money. Some ports are worse than others, so expect it.
