For 2012 the best advice we can give is book your cruise sooner rather than later.
In March of 2011, Raye & I cruised on the Allure of the Seas, with the inaugural stop in Falmouth, Jamaica. We were so impressed with the ship, when we got home, we immediately booked our entire family ( 10 of us ) on the sister ship Oasis of the Seas, for February 2012. Prices since then have gone up significantly. Booking early saved us hundreds of dollars.
We are also seeing higher prices for other sailings next year. Prices are rising faster than the tides and we don't expect to see a lot of deep discounting by the major cruise line brands in 2012.
If you are waiting for lower prices, you may likely find a higher price and less of a choice of popular accommodations onboard. The best staterooms ,mid-ship, balcony and prime ocean view locations may already be sold.
Wait to the last minute and you'll have trouble finding affordable flights, as many airlines have cut back their capacity to save money. If you plan on cruising overseas, now is definitely the time to book your cruise and secure your air flights. It's going to get very expensive and difficult to find the best flights, times and prices, the closer you get to your sailing date.
So, our best advice, book early. If the cruise lines do offer a better deal down the road, you can always ask your Travel Agent to contact the line and ask for a price reduction for your cruise. It doesn't happen all the time, but in some cases you can get the prevailing lower rate.