I assume you were talking about Carnival cruise line.

Try to avoid the deck directly above or underneath the public area, but if you get seasick easily, the lower deck, the more stable, hence less chance to get seasick. Also, in general, the mid ship is more stable than the forward/afterward. You can also consider book the inside room instead of the one with balcony to be able to save money. You will spend most of your time at the public area or on the shore anyway, the cabin is just for night sleep.