If you go to the main restaurants which are free no you do not have to make reservations,just show up whenever you want,early no lines,late no lines,go about 7-8 might have to wait in line 10 minutes max! The specialty restaurants you do have to pay for like Le Bistro,or Cagneys,and make reservations as they only hold so many people,you will get a freestyle newspaper every day in your stateroom,they usually put it out at night on your bed,you can call ahead to make reservations at night for these restaurants for the next day,or in the atruim lobby they have a set up where you can read daily menus in restaurants and call in to reserve,or you can stop at the places when you are making a tour of the ship the first day you are on and make reservations for the paid ones. Le Bistro usually has half off the price the first evening which is 15 dollars a person so you would only pay 15 dollars for both of you and I think its the best fee restaurant on NCL and on the Dawn in Le Bistro if you are into Art they have real Art by famous artists on the wall,Monet,Picasso ect.
We have done both booked excursions on ship and off,if it is a safe excursion its cheaper to do off but more dangerous I would do ships excursion plus if you are late back they will not leave without you because ship excusion made you late! Hope this helps,I would enjoy the free restaurants,the grills poolside are great,the chocolate midnight buffet is a treat and there is free room service as well,just remember to tip the guy that brings your food up! Enjoy and happy sails!