I ALWAYS check the smoking policy.
Some are much more stringent.I now sail on ones the LIMIT smoking to few,certain areas..NOT IN CABIN OR BALCONY>
Really prefer ones that have room service 24hrs.at no extra cost.Such a luxury.
Find out HOW MANY PASSENGERS,,big difference in wait times and service.Found I prefer the 700 size(seems just right).
Do find exactly WHAT is inc.in price,,,some have(luxury or similar,sure)EVERYTHING inc....even drinks,excursions,tips,you name it. Then others you must PAY FOR everything.So add it up,,whats best for you??
Consider alternative to just OCEAN cruises,,have found river cruises great too(alternate between the 2 now,,see best of both worlds.
Really study member reviews.Look at you tube,etc.Lots of info out there.