If you’re going to smuggle booze on board, and you should, it’s easier to get on board at the beginning of the cruise rather than at ports of call.
Usually a few events (like at the casino or during sales presentations) will have free drinks like champagne or rum punch. Go in, slam down your drinks (they’ll run out fast), and don’t buy anything. 
Our ship had a newsletter with activities every day. That was helpful.
Bring books, eventually you will want some downtime.
Never do the buffet. Always formal dine. You will avoid the gaggle of kids and the food is much better. There is often MORE choice (and fewer of yesterday’s leftovers).
Shore excursions are nice but I actually had more fun on board – I love to travel to new places, but the port areas are usually overly touristy and with no real local flavor.
The chocolate buffet that they always seem to have is incredibly overrated. The food quality is really pretty awful (far lower than the normal desserts because people shove stuff into their craws so fast). We waited in a huge line for a long time, it was completely not worth it. Pretty, but not worth it.
The food’s free; be adventurous, and be nice to your waiters. You will see them every day after all!
They don’t give you that much food, so after a long day of physical activity, we would always order appetizer, salad, dinner, and dessert to be satisfied when at formal dining. Portion sizes are much smaller than typical American restaurants. They will actually bring you two entrees or salads or whatever if you ask. We laughed a lot when my sister accidentally ordered – and received to her surprise – two entrees, but towards the end of the cruise, many in our party would order double appetizers or desserts just to get to try everything (some things are VERY small).
The lifeboat station thing is generally done as a shipwide drill on the first day. We had to go out in our lifejackets and all.
Onboard stuff is usually overly expensive, but I actually picked up a few things “on sale” toward the end of the cruise - a nice wallet for example, that I still use, was $5, and an inexpensive beach hat when I realized I didn’t want to burn so badly.
If there is anything by reservation - decide quickly and reserve! We missed the chance for the small additional charge ($10) restaurants.