I've got quite a bit of experience with motion sickness -- while I get seasick drinking a glass of water, I have a wife and daughter who love the sea. Here's what I've learned in all these years (in no particular order):
Food. Life is easier on a full stomach but the meal should be carbos and *NOT* fat. I've heard that studies say protein is best (but only if you can do it without fat). Me? I likes me some carbos.
The Horizon. I've *not* gotten a lot of help from looking at the horizon. On the other hand, close focus and using fine motor skills will make you wish you were dead.
Limiting Sensory Input. Limit sensory input. Smells are bad, bad smells are evil, aside from the obvious (biologicals), engine smell (e.g., diesel) is abyssmal. I've found that closing my eyes can help (but not if your head is swinging wildly about). I really prefer it if noone trys to talk to me (especially to tell me what works for them). Don't even play music.
Relax. Pay attention to the stress in your shoulders and actively relax them.
Sea Bands. Sea bands have never helped me. They do, however, irritate that little area where the button rubs a hole in your skin.
Cool Air. Cool air in the face helps a _bunch_. Drinking cold water is really helpful. Warmth is death.
Medicine. Medicines work differently for different people. Scopolomine and its oral cousin, Scopace, work best (by a long shot) for me. A distance second is Bonine/antivert. Dramamine just makes me sleepy. Ginger (particularly Trader Joe's candied ginger -- the stuff from Australia rather than the stuff from china) works well to get rid of the nausea but my motion sickness starts as dizzyness in the head. For that reason, ginger doesn't do it for me.
Sleep. Nothing works better than sleep to eliminate existing motion sickness.
Where On The Boat. Surprisingly, where I am in relation to the boat is of little value (except, as mentioned before, keep away from anything that generates a smell).
Vibration. Vibration aggrivates motion sickness as does facing away from the direction of motion.
Horisontal. Laying down (with the head supported) helps a lot.
Sea Legs. Some people get sea legs in a couple hours, for some it takes days, and for others relief never comes. My father-in-law worked on submarines in the Navy and he knew people who stood watch every night of an entire tour of duty with a bucket between their legs. For me, it lasts at least three days -- I haven't had occasion to try it for longer than that.
Compazine. When all else fails, Compazine suppositories work wonders. I was in 15 ft. seas in the Drake passage on Scopolomine, prescription antivert, ginger, wearing sea bands, laying down, letting (very) cold air hit me in the face, and throwing-up. One suppository let me get to sleep and deal with it.