I actually make a list for each day and figure out in my wardrobe what we are going to wear, lay it out in piles and then pack it! The list really helped me on our cruise last year from overpacking and didn't have much that we didn't wear! I'll do the same for our upcoming cruise.
Now, our daughter and daughter in law - that's a different story!! Our daughter has to pack a million pairs of shoes and lots of clothes changes - trying to get her to make a list of clothes - she made a list for other stuff, but not the clothes!
I know on the ship we can use the laundry room - however, I don't want to be bothered with domestic chores while I'm cruisin, so I make sure I pack enough clothes for each day!