I have done this twice.
There are transfers outside of the arrivals terminal, you buy your ticket and away you go,its about a 1/2 to 3/4 mini bus ride, depending upon the number of stops along the way.
I am also considering a cruise that sails out of Ft Lauderdale. I will be flying into Miami. I am traveling solo, so a shuttle would probably be less expensive than a taxi. I would appreciate any specific info on a shuttle service--rates? company? Thanks.