In my early days I would often order a second appetizer or entree. That lasted about three or four cruises.
Since then I rarely order more than one entree but often will have an additional appetizer. i.e. salad and hot appetizer.
If there is a pasta entree my wife and I may order one of those and share it along with our own entrees.
I have never been given a second glance when ordering a second of anything.