First, start with a 1/2 day boat. If one of your party isn't happy or is experiencing sea sickness it best to have as short a day as possible.
Don't buy any tackle, most boats or landing have rigs to rent.
Try to understand the culture, and "do" listen to the deck hands. When in doubt ask. Most boats have a rotation along the stern to give all an equal chance. But, and it's a big one, it seems every boat has one or two barnacles. They are on the boat regularly (some times everyday) and they have "their" spot. Ignore them and just enjoy the day.
With regard to sea sickness, Dramamine still works, but it must be taken before onset, and can make one drowsy. There are new and better over the counter meds that will reduce the symptoms (sometime entirely) if taken after onset. Honestly if it's your first time or your first time in a while, take it before. Why take a chance on ruining a great day on the water.