You don't have to be on at midnight but if there's an excursion or an earlier PAT you're hoping to get, it's best to get on as soon as you can. You can look through the available excursions for your itinerary now, research them and make note of what you want. For us, I do stay up and check in as soon as our booking window opens up because an early PAT, brunch and dinner at Palo and a possible cabana at CC are very important to me.
To help with the planning process, go through some of the navigators posted online from recent sailings with the same itinerary. This will give you an idea of what activities are offered on board and what the typical schedule looks like. Also download the navigator app at home before you leave for the port. When you get on the ship, open it up.
Once you're on the ship, if the princess meet and greet is important to you, go get those tickets. Some people like to bring their swim suits and head straight for the pool so they can enjoy that while it's a little less busy. We usually go straight to lunch and then head to our room as soon as it's read to unpack. It's nice to be all unpacked before the ship even leaves port.
Honestly, it is very possible to over plan. We didn't plan very well for our first cruise and left feeling like we missed a lot and I over compensated for our second. Figure out a few things that you really want to do and allow yourself down time. You won't get everything done on your first trip but that's ok. It leaves more to look forward to on your next cruises.
