Overall, Sapphire is an excellent ship. I researched quite a bit on this site and others and went prepared as well as I could. From my perspective as a second cruiser staying in an ocean view room, this is what I'm glad I did or didn't do. Some of it's specific to Sapphire, some not.
1. I'm glad I brought my cell phone. Clocks are hard to find on board.
2. Making a budget and putting a decided amount of money into envelopes for excursions, cabs, tips, souvenirs, and whatever else you like. Kept a rein on my spending and actually had money left over!
3. I brought a carry-on suitcase and was able to wheel it on at embarkation instead of waiting hours for my luggage to arrive.
4. Did express checkout (carry own bags). I had to meet earlier than others who had their luggage picked up the night before but we zipped out of the parking lot while others were still waiting on the ship.
5. Take showers in the spa. It was three times the size of my stateroom shower. You don't have to have a spa service to do this.
6. I'm glad I didn't bring duct tape or a power surge strip. If you need duct tape, buy better luggage or tell your room steward to fix whatever it is that won't keep open/closed in your room. The strip isn't needed unless you have a lot of things to plug in at once. Lastly, I wish I would have brought walkie-talkies. More efficient than leaving post-its in the room.
Regarding excursions, I swam with the dolphins in PV and rode horses in Mazatlan. Let me know if you have any specific questions!