Ok, now I have more time...
Join the FE group on your cruise - it is so much fun. Some people went all out with the FEs and gifts but others on our group used a simple felt bag on their fish. Don't feel you have to out-do others, I bought heaps of little stuff from the dollar store once there with some cute ziplock bags to put them in. I also made magnets, calendars and book marks using my printer at home, plus bought heaps of Aussie stuff like stickers, magnets, key rings and koalas after Australia Day to add to my collection of things to give out.
Don't overplan your day onboard, especially if you have children. Be amazed by the unexpected (characters also pop up out of the blue in the most unlikely places without notice) and be prepared to relax, have fun and take things as they come.
Don't take yourself seriously - way too many people do and it just causes stress, just go with the flow.
Formal nights and dressing up is not as big a deal on
DCL as some other cruise lines make it out to be. On our last cruise we'd wear a nice dress (girls) and the boys/men would wear jeans and a nice shirt to formal night - we were away for almost 2 months and had to economise on our luggage. On every other night you could easily get away with dress shorts and a nice top. The family who were seated at the table beside us were often in tracksuits or shorts.
CMs will often be happy to take a photo of you with the characters using your own camera if you ask. The photographer can't. If you don't have a CM there to assist (it happens) then someone else waiting in line is usually happy to help.
Buy a plastic shoe hanger and an S hook to hang over the bath room door - ours carried brushes, batteries, p&s cameras when not in use, hair bands, lanyards when not using them and lots more. Everything was in one spot and easily accessible and kept the room tidy. There is not that much bench space or storage space in a cabin when you have children.
Buy a pop up laundry hamper from the dollar store before you get on the cruise - we'd put all of our dirty laundry in there and I washed about twice on the cruise. You can always throw the hamper out at the end of the cruise to save on space. I saved up heaps of the sample laundry powders that came in magazines throughout the year to use as we travelled, but you can buy powder etc onboard using your room card which is linked to your account. On the Wonder it was $1 for the washers, dryers, powders, softeners etc.
Buy luggage than can stack inside each other - I had two large and two slightly smaller suitcases plus soft bags and we could fit them all in the wardrobe or under the bed.
As soon as you get on board go straight to Guest Services and ask what you can sign up for. I knew about the Tea and Gingerbread house making in advance - these book out quickly and there is often a wait-list by about 1pm for them. For the tea I signed up the 4 of us but in the end hubby and my son didn't want to participate so I sought out members of our FE group and gave my spare tickets to the first two I spotted.
Bingo is fun but expensive. You don't need bingo dabbers though as they have perforations in them to push the numbers out.
If you have anything you want to 'gift' your room attendant with the exception of regular tips of lollies (we gave him DDs pirate costume for his daughter) you must write a note advising this so he/she can pass it on to someone.
If you don't like crushes and jostling for tables, eat your meals in the dining rooms rather than the buffets. Or get there either at the start or end of the buffet times. On P&O we would often find ourselves sitting on the ground at the side of the ship to eat as we couldn't get a table until we realised it's less of a hassle in the dining room. It wasn't so bad last time on the Wonder but we preferred eating in the dining room.
My kids found the ice cream cones on the deck were on the small side and the heat made them drip quickly so they would get a drink cup from the other side of the deck and use that to put their ice creams in - no drips and less trips to get a top up
But most of all, just have fun. You're there to have a fun and relaxing time.