I booked in April for an August 22.2007 Jewels of Europe cruise. I checked to see if there were any changes and found that the prices had gone up.Book as early as possible so taht you can get the tour that you really want.
Depending upon the itinerary, usually 60 to 120 days prior to the cruise you can book shore excursions. Just make sure your TA gives you your booking number. You'll need that to gain access to the shore excursion booking engine.