Blythe is correct. Do some research though as you can often do your own thing for MUCH less and at a different time to all the coaches and leave the crowds behind ! Book shore excursions on the Princess site (internet) and cancel those you find alternatives for (such as taxi)when you get on board. Just drop a note into the shore excursions 'Drop Box' by the desk.
If there any tours you particularly want to go on then the answer is Yes. You can cancel later on but there is a charge for doing this. I suggest you check their web site for details on this.
The advantage of booking ahead should guarantee you places on the trips you really fancy doing, but should you have to cancel and with our trips in the past if you give reasonable notice you get a refund on your stateroom account. This migth not be the same with all cruise lines but the booking information you see on-line should advsie you of this.
Yes,definitely book ahead as,when we got on board Sea Princess, some had already sold out.You can always change your mind and cancel as long as you do it before the 'closing' date and get a full refund.You can book up online which is what we did and then printed out our list of trips and costs for future reference.
We booked all our tours in order to be certain. it also saves a lot of queuing when on board. They are pricy and often you can get cheaper by getting a local tour dockside when you get to port. but booking the princess tours guarantees you wont miss the boat when it sails.
Yes book early as the most popular tours will sell out. While there will be tours availble on display in the Atrium its always best to sort your trips early to avoid disappointmen.