What advice on decks? If you are talking about you should be on deck 2 and in the middle well only so many people can be there.
Exact opposite I say, mid deck, mid ship, deck 2 is the very worst place to be, the waves have small random movements there, higher up its a long sway. You need fresh air and view the horizon.
Being next to the sea, the waves and movement, and the engines is the worst place, science shows the further away from anything the better, now sickness is caused by the ear detecting movement and your eyes telling your brain, walls do not move. View the horizon and it all works it self out.
Things like, the type of waves, the current, the direct of current to ship, the wind, the wind go the ship, the stabilisers, the ballast, IE water to stabilise all have an effect, no cruise is the same.
We found Animators palate the worst, inside, low deck, small random juddering, and aft near engines and thrusters.