DONT!! i went on one to mexico last year and it totally sucked. i mean it was pretty cool being on such an awesome boat, but it was full of old people (holland america line). after the first day or two, i was pretty bored with what the boat had to offer. and when i went on shore, it was a HUGE tourist trap. overall, the trip sucked and was overpriced, but the free food was nice. 

I’ve been on two short cruises.  The first to the Bahamas.  The ports of call were relatively interesting although the shore excursions were overpriced.  I loved the cruise line’s private island.  Absolutely beautiful, uncrowded beaches and the the best snorkeling ever.  The reef was wade out, swim two strokes and you’re there, from the shore and absolutely fasinating.  However, I didn’t care for the on-board entertainment, and I think you really have to enjoy that sort of thing to really get your money’s worth.  I absolutely hated the bow and scrape, lick your shoes attitude of the staff.  People hovering around to answer your every wish is stiffling.

The second was a much less luxurious Greek Island cruise.  I enjoyed the ports of call, and the good, though less regal service.   Compared to the total for ferries, hotels and meals it really wasn’t that expensive for island hopping.  Further, we had a very limited amount of time for this trip, so not having to deal with the logistics of ferry schedules meant we could see more.  However, it’s like a tour.  You meet your shipmates, not locals.  You tend to follow the group and be herded to the totally touristy things instead of doing your own thing. 

I’ve been in two cruises, too. One short, one longer.
The in-laws paid for the first one. It was on a humungous ship through the Bahamas, and to me the ports of call were just okay. My cruise experience basically was the same as what oldlady describes. It was really good in terms of having a family reunion where everyone could just go off and do what they wanted.

I really enjoyed the second cruise, but it was a completely different type. It was on a crewed catamaran with other family members.
We sailed through the British Virgin Islands for about 8 days. There was scuba and snorkeling.
The BVI were absolutely beautiful and the locals we met were wonderful—I would definitely return there.
There were two catamarans and about 12 people. There were tons of food and drink. This cost thousands of dollars.

I did a Norwegian Cruise for a week, me and my mate didn’t know what to do for our birthdays, so we booked this cruise, it was the cheapest cruise we could find, and that reflected in the service, while everyone was grabing seats for the shows, we were just getting our main meals, all-in-all, it was more of a ‘Carry On Cruising’ Cruise, lots of drinking and dancing

No desire to go on a cruise ship.  It seems a waste to me.  My idea of a trip is to see the culture of a country.