After literally thousands of days and nights at sea these are the steps that have worked for me:
No alcohol for a few days before you sail.
Start taking your anti-puke a day before you sail.
Simple foods before/during the trip, but make sure you keep your stomach full and try to stay hydrated.
Stay upwind/away from any exhaust fumes (unless it's time to puke, in which case try to puke downwind)
Focus on the horizon/don't look down when outside.
Minimize inside time as much as possible. If you have to be inside/it's dark, try to find the most stable part of the boat. A V-berth in the bow is generally worse/pitchy than a midships bunk, and I'll sleep on deck or in the lounge if it's the better option.
The progression generally goes from fine to yawning to sleepy to kill me now, and gets worse faster than it gets better unless you find calmer water or get back to shore or you eventually get your sea legs which can take from hours to days to never.
Of course YMMV and everyone's different.
My last worst night at sea was documented here (minute 10+)