I’ve been on P&O, there is usually one formal night per week on a cruise - you don’t have to attend though - the dress code only applies if you are going to one of the main dining rooms or speciality restaurants on these nights - you can choose to go more casual and attend the buffet or take away area instead. You don’t need to wear a dress though - a skirt and blouse, or tailored trousers and a top would still be acceptable. Some people like to get dressed up every evening, but it’s a personal choice.
We took packing cubes, which was very handy, as our cabin did not have drawers, only cupboards with shelves, but there was plenty hanging space in the wardrobe as well. Suitcases fit under the bed, where we put our dirty washing - there are washing machines and dryers on every floor which are free to use - this was great as it meant I didn’t have to do all my washing when I got home - take your own detergent (I used the laundry leaves by Dr Beckman).
Book entertainment before you go - I think the bookings opened up a couple of weeks before - we booked the Limelight Club and other entertainment before we went - they sell out pretty quickly. We never managed to go to the small live music venue at all (can’t remember the name - the 778 club or something) as it was always sold out - it’s very popular, it seemed to have only midnight availability which was too late for us if we had an excursion the next day.
if you attend the Limelight Club, head down to the entrance at least 1/2 hour before, as people start queuing early - tables are allocated nearer the stage for the first ones in the queue.
We enjoyed sitting in the bar beside the library, as it was much quieter and relaxing to have a drink than other places, which could get very noisy and busy.
We didn’t get the drinks package, as we didn’t feel it was worth our while. You are able to take a bottle of wine or champagne each on board - you can also order a bottle of spirits from room service, which isn’t expensive - you can ask for that to be delivered with an ice bucket - you’re allowed to take soft drinks on board with you, which you can keep in the fridge, so it was nice to be able to have a gin and tonic in the room while getting ready, or a cool drink after a hot day offshore.
if you have Facebook, there will be a cruise group set up for the cruise you are going on - search for the cruise ID and you will find it. It can be useful, but also contains a lot of things we weren’t interested in, like people wanting to hide ducks for people to find etc.
If I think of any other tips, I’ll let you know. Happy cruising!