The general advise is to pick the bare necessities in a carry on and let the staff deal with everything else. In you carry on you want to have any medications or other valuables you may need as well as a swim suit and cover up if you want to get wet. You may not see you luggage until after dinner.
A Bad Day At Sea [with power] Always Beats A Good Day At Work
Carnival: Glory 2004, Destiny 2008, Splendor 2009, Freedom 2011, Valor 2012, Dream 2013
Celebrity: Summit 2011
Princess: Ruby 2010, 2014, Caribbean 2013, Coral 2014