My wife, daughters (12 & 9) and I travelled on the Navigator of the Seas for a 7 day cruise on 30th May. We are all first time cruisers so here are a few tips that may help other newcomers to cruising or to Royal Caribbean.
What to Pack: Forget the guides. Take as little as possible for dining and focus on light wear for daytime. Men wore the same for Smart Casual as well as Smart. As long as no Jeans or T-shirts it's fine. 1 Suit or Tux for Formal is all that is needed. Ladies a couple of "glam" outfits but again the rest light casual dresses will do. Do not pack towels, face cloths etc... as all obviously provided and towels can go off ship too. We could have packed a 1/3 less if we had known and you need the room with the extras you bring back especially if you have kids.
Dining: We only went to the Main Dining room and not the speciality restaurants. Service was brilliant and Omar our waiter even did magic tricks. We were paired with another family who lived within 30 miles of us so be prepared for that. It's nice to meet new people. The food quality was very good and the amount was huge. If you have kids that do not do restaurant food much they may find it a little "rich". We also ate our evening meal a couple of times in the Windjammer where there is such a huge variety that nobody could possibly not find something they liked. The Windjammer at lunch times can be chaotic and trying to find tables can be hard. The staff work so hard cleaning tables and replenishing food.