We use one suitcase as the dirty clothes hamper, that way it is all packed and ready to go on the last day. All we have to do is put the rest of the clean clothes (we always bring too many clothes) and the rest of the stuff we have accumulated on the ship in the other suitcase.
We use a lawn and garden size plastic bag for dirty laundry. Just throw it on the floor in the closet. When it's time to pack for the return trip home use the plastic bag to separate the dirty clothes from the other stuff.
I take an extra duffle bag in the bottom of my suitcase and fill it full. Zip it up and check it in on the way home. Works really well and have all the extra space for my stuff that I bought to take home.
I have nice airtight bags I got from Magellens to pack my clothes in on the way. They are zip lock and you roll them up to get all the air out. Really, everything comes out pretty wrinkle-free if you fold them nicely. Then I use these for dirty clothes on the way home. Seems like the dirty clothes take up so much more room, I guess because they aren't folded. I keep a garbage bag in the cabin to hold them through the week, then transfer them to the airtight bag for travel home. Less wasted space.
I FOLD the dirties and put them into an under-bed suitcase. When it comes time to repack, I put cleans on the bottom of the suitcase (there are ALWAYS a lot of cleans), put a plastic bag over the cleans, then pack the dirties.
We have a nylon army duffle bag that I hang on the back of the bathroom door or what ever door will hold it. I stuff all of the dirty clothes in there, send it back home as luggage and when I do the laundry, I wash the duffle bag also. It folds up quite small thus leaving me a lot of room in my suitcase for purchases. Dawn,Ct.
I put dirty socks and underthings in the outside pockets of my suitcase. Those pockets don't lock, but I figured if airline personnel wanted the dirty stuff, they could have it! Doing this left room in my suitcase for souvenirs. The dirty outer clothes I folded up and put back in the suitcase and it was more efficient space wise. By doing this everyday, packing to leave the ship was a snap, as I was already halfway there!