For most cases it doesn't really matter. However if seas were rough then it is ironic that the cheapeast cabins (those on deck 2) ride better than the expensive cabins on deck 10. Cabins on the lowest deck and closest to the ships centerline have the least amount of felt motion.
But seas rough enough to make a noticeable difference in cabin ride are rare (at least to me), so I really wouldn't worry about it. I typically try to get a cabin close to the pool deck since I hang out there. I'd be more concerned with keeping in mind what is above and below my cabin - such as a running track or a lounge with live music. These can give you more of a problem than the motion of the ship.
I have been in rooms from the front to the back. I am not prone to sea sickness, so it makes no difference. If you are, stay in the center and low.
I agree with Dave56, When I book a room I am more concerned about what is located above and below my cabin. I am a lite sleeper and any noise will wake me up. I had one cruise where they rolled a heavy cart across the deck above me every night between midnight and 1:00 AM.
If it is because of sea sickness that you are concerned with the location then do not worry. The RCCL ships have state of the art stablizers and the trip is very smooth. I have been on 20 foot seas on the Mariner and you could barely tell it. So do not worry. Just plan on having a great time and you will.