obD:
Bryan's right. As an inveterate cruiser myself (I'm heading out on my 13th over Thanksgiving), I've got all sorts of advice, but the bottom line for first timers is to find a trusted travel agent (the Auto Club is probably the best known, but not necessarily the best), to pick the brains of anyone you meet who has ever cruised, and to think long and hard about the "atmosphere" you think you might like.
Without going into any great detail here, I'll observe that many Villagers travel with other Villagers. There are many who sail with Carnival. My image of Carnival may be jaded, but they're popular because they're frequently inexpensive (no cruise line should be considered "cheap," really), but they are honestly geared to the "younger generation." That is, the 20's, 30's and 40's crowd. Us "old folks" are usually more comfortable on less "party, party, 'til you drop" ships. As an example, are you into "hairy chest contests," or their equivalent, "wet tee-shirt contests?"
Of course, one of the first things you must think about
: have you even the slightest propensity toward seasickness? Modern cruise ships rarely pitch and roll enough to be concerned about, but if a simple ferry crossing makes you queasy, you may want to think again. If you've got some doubts, there are remedies which many folks rave about.
And, it's never a bad idea to consider one of the three-night or four-night cruises first. They'll give you a clue as to whether you like cruising, and won't upset your four-legged friends so much!
As a retired travel agent and as an avid traveler and cruiser myself, I'm always happy to tell you my personal thoughts. And, am always (unless I'm cruising

) willing to spout off at the mouth! Just PM me.
SWR