Before my first cruise I found a number of cruise packing lists both online and in various guide books at the library. I consolidated them, removing any items that didn't apply to me, and then I tailored it to the cruise itinerary I was going on. Like others, I looked at my planned activities for each day and chose my clothing accordingly. I don't bring extras for contingencies; I'll just make do as necessary.
Before the cruise I do a prepack a few days prior to (1) make sure I've got everything I need, and (2) that it all fits in my suitcase without danger of an explosion (or being tagged with an overweight charge at the airport). I lay things out for each day as it's easier for me to visualize if I'm missing anything. I then unpack the clothing to reduce wrinkling, leaving everything else in my bag so I don't need to track it down again.
When I unpack in our cabin, everything goes either in the drawers or the closet, and the suitcase goes under the bed. Every couple of days I repack anything that I won't be wearing again. When it comes time to repack, I empty out the drawers and closet, then put back anything I'll need for the last night and disembarkation, and what is left gets packed.
When I get home I go over my packing list, noting items that were too many or too few (or not at all). I rarely make any changes now and I rarely bring too much or too little.
