When we took our first cruise we had been at WDW for about a week and were looking forward to the cruise. Not knowing what to expect, we went to a park for a few hours in the morning, came back to our room and finished packing the car for the trip over to the port. Since boarding didn't start until 1 (officially) I decided we should have lunch at the hotel before we left (it was after lunch time when we could board the ship and we would have to wait until dinner to eat - wrong wrong, wrong!!). So we got to the port late, had lunch again (the buffet), rushed around looking at the ship, did the safety drill, got ready for dinner - whew!!
The right way to do it is: catch the earliest bus over to the port (I assume you have the land/sea package). Enjoy the terminal, board the ship as soon as possible, make Palo and spa reservations as needed, enjoy the buffett, explore the ship (or bring your swim suits in your carryon bags and go swimming - the pools will be at their least crowdedness) and enjoy. The whole key to this is the same as at the parks, get started early!!
Have a great trip!