You can preorder excursion tickets, tuxedos, flowers, wine, and as previous poster noted all sorts of packages. Unless you really want a specific spa package I would wait till I was on board. Not everyone signs up for these as they can be time-consuming and costly. Thus the spa will often offer "last minute" specials and knock some of the price off or even offer two for one specials to get couples in. We have found the flowers available on board to be disappointing and pricey. The quality of the flowers is good but we are mystified that in the midst of Caribbean splendor, the shop offers carnations and roses! On some islands you can get great tropical flowers at local shops for a reasonable cost to brighten up your room. You will have to leave them behind when you leave (customs regs).