just got back from my first blackbeard's trip, which was also my first liveaboard. this thread was invaluable, and most of the advice was useful. Main things:
1) Take 1/4th of the clothes you would think you need
2) lots of sunscreen
3) either take seasickness meds if you are prone to it, OR just get up and start talking and making friends - i found the latter worked best for me
4) Great food, GREAT MUFFINS after the morning dive!!
5) Fishing was good, but not special - but its a dive trip, and the diving was definitely special.
6) either take a book, or be prepared to talk a lot - there isnt much else to do on the boat
7) clothes pins are provided - i took some of mine in any case, but they were no way strong enough to hold onto a wet wetsuit when the sea winds are blowing - if you are taking your own, buy some heavy duty ones, not the small wooden ones.
Apart from that, it was truly a fantastic trip - the diving is excellent, the Blue Hole and drift dives are works of art, and the crew is fun. WOuld do it again in a heartbeat.