Disney has a well integrated system--they usually know that you are a DVC member whether you are sailing on points or on money. There is a DVC desk in the terminal--you can check in there before sailing or at the desk on deck 4 to be sure they have you on the list.
You will be invited to a DVC member gathering which will include an update on member benefits, door prizes, and refreshments. You will also be invited to attend the "open" meeting (a sales pitch explanation of DVC intened for non-members) which usually includes a "members only" door prize drawing in addition to door prizes for non-members.
You will typically receive a magnet on your stateroom door (then you know you're on their list), and sometimes hats and pins. Sometimes there are no pins, sometimes there is one per day...varies with who's representing DVC on board.