Identify your cabin steward.  He will can show you how everything works and what to expect from him.  A friendly cabin steward can be very helpful.

Unpack your luggage as soon as you can.  Get it over with and allow more room in your cabin.

Confirm that your meal seating confirmation information is in the cabin.  If it's not what you requested, see the Maitre d’ as soon as possible.

Find out when the lifeboat drills are scheduled and be ready to participate.

Find out where the spa, salon or babysitting service is located and sign up before all the good times are gone. .

Re-confirm your shore excursion plans to verify that you are definitely going on the ones that you want.   If you haven't pr-booked, sign up now before they sell out.

No.  Cruise lines have developed a billing system that is very convenient.  Upon check-in, they will take an imprint of your credit card and set up a kind of  tab for the length of the cruise.  Your total bill will be presented to you at the end of the cruise.  Always keep the little receipts that you sign and verify the charges at the end.

A major credit card, traveler’s checks or a substantial cash deposit will usually suffice to set up your account on ships sailing from U.S. ports.

Often, personal checks are not accepted.  When they are,  they probably will have strict limits.  Check the line’s policy if you plan to use this option.