We have sort of evolved over the years on our cabin selections. Initially, on our first in 1990, we booked an inside but just before boarding they upgraded us to a "porthole", yes, a real porthole with the big latch screw bolts and all. Loved it and the fact they did so left a good taste which kicked off and a wonderful voyage, Princess.
After that we always booked an outside cabin, didn't care which deck, fore or aft, except didn't want to be low in the stern over the shaft alleys and screws. Some worry about being too far forward and able to hear the anchor chain, I always thought that rather silly, since they rarely drop the anchor and when they do it is for a tender port usually around 7 AM to 9 AM, if I haven't already been up by that time then I need to be, Haw. In Singapore, 2007, the inevitable happened, HAL offered us a deal for an upgrade to a balcony. We knew if we took it we would be spoiled and never satisfied without, we did and we are. Don't book anymore unless we get one. Also, we prefer the mini-suites over a plain balcony cabin. Reason, we like the couch, wife likes to get up in the middle of the night and read, she can pull the curtain, turn the lights on and have a room all to herself.
As previously mentioned, the best location is down low and mid-ship particularly if one is susceptible to motion sickness. We aren't but down low has its advantages other than that, I like to sit on the balcony and watch the flying fish, therapeutic, so being closer to the water makes that nicer, also, better fish viewing the further forward as they come off the bow wave. However, I don't mind being up high either, but I don't like a balcony where I can't look straight down the side of the ship into the water. Set back cabins overlook other's balconies. I don't really mind those up above and behind us seeing part of our balcony but I want to be as far out on the beam of the vessel as possible.
Much is said about staying away from cabins that are close to the laundry, elevator towers, utility rooms, below the pool deck (lido), etc. I believe that to be good advice, except, so much depends upon the ship. We have been close to all of the above without any noise problem at all. For instance, in October we were booked out of Lisbon on a TA, they gave us an offer we couldn't refuse and that was to tack on 10 days in front making it a B-to-B, leaving from Rome instead. Trouble was our TA mini was already booked to Lisbon so we would have had to switch rooms, been there done that, don't like it. But they had a mini two decks up available all the way, under the lido though. Took it and it turned out we hardly heard a thing all cruise, I even paced off the distance from our room to the elevator then did the same on the lido and we were right under tables etc. No complaints what so ever, lucked out I guess but then it might have been the ship's construction.