Apparently the electronic Reliefbands work. I was skeptical myself and assumed it was mostly placebo the first time I went with a friend using them, but now I have had 4 out of 4 friends who I have watch get seasick on every single prior boat trip have sucess with these. One was fine until he took them off to gear up, then got as sick as ever and only did the first dive. 1 reported feeling queasy during the surface interval, but did not get sick. The other two had NO symptoms and these are people who get sick watching a merry-go-round! I have NO idea how they work, but they seem to be the most effective, (and the most expensive) treatment. Maybe BillP knows of some randomized studies--I don't-- I can only offer my experience, but if they are available where you are, I suspect it would be worth the investment.
For standard tips, I agree with the prior posters and would add to make sure you avoid the boat exhaust while you are in the fresh air, and along with trying to have you gear ready, I would generalize to try to avoid doing anything requiring concentration after pulling away from the dock
Good luck!