First time cruise for wife’s 60th

This review is for the booking process only as the cruise is not until March 2019. This was completed most efficiently over the telephone, advising me of the different cabin options, when I asked, over and above the basic, base price, one. As a result I changed from a porthole cabin on deck 5 to a balcony one on deck 14, just about midship. After booking, the agent gave me his direct phone number and email in case I had or have any questions. The next day I sent a message regarding the need for visas to which he responded almost straight away, including a web link. I am very impressed. Of course, we will only find out if we have a good stateroom, a good cruise, etc., once there, but so far so very good!
Never having been on a cruise ship I have no knowledge, apart from television programmes, where they always show the very best cabins, of what is best to fit with my budget. Near the front, near the back, a high deck or a low one, is a balcony worthwhile, is one part of the ship quieter/better than another, etc., etc.
We are going on a Norwegian Lines 7 night cruise from New Orleans to Mexico, Belize and back, preceded by 2 nights in Memphis and Nother 2 in New Orleans.