I have heard and read that some cruisers are generous and tip extra to some staff like the cabin steward,waiter and assistant in the dining room, various bartenders,etc. Apparently these tips help the passenger to receice a little(or a lot) of extra attention. Is anyone familiar with this practice and how much would be enough and not insulting to the staff? Also, how does the staff know that you have prepaid gratuities and that we just didn't ignore the envelopes left for you on the last night? Thanks to anyone who can answer.