Having said that. I may actually be able to give you some advice, having just done my first liveaboard in early April.
Mistake one, I brought way to much stuff!! - whatever you are bringing, drop it by half...I found I really only needed two or three pair of shorts, about the same in t-shirts....shoes? not really...just some flip flops. Clothes are not necessary, you will be in a swimsuit for the vast majority of the trip.
The crew (at least on the T&C Explorer) love new books, music (I swapped about 5 GIG of music w/the crew), movies and any updates on reality TV shows (couldn't understand it, but they were jonesing for updates on Survivor, American Idol, etc). Bring something along they will enjoy.
Be nice to the crew. They will wait on you hand and foot and have a smile througout (despite being on the boat six days a week for the last 7 months). I was amazed at what great attitudes they had and always kept that in mind on the few occassions that I had to ask for something that should have been set already (example, tank a few hundred pounds light, etc).
Relax and enjoy...I had a blast!!! Which explains why I am now asking you about your planned Nekton trip. Liveaboards are the way to go!!!
If I think of anything else I'll let you know. There are many others on this board who have done tons of these and will be able to give you better info.
Jeff