When you move belowdecks, can you stand up straight? True standing headroom means there's at least 6'1" of vertical clearance.
Test carpeting that isn't glued down by folding it over on itself. The best, heavy-duty carpeting will be too thick to fold easily or crease, so it will wear well over time.
BOUNCE FOR THE BUCK
When you sit on the salon lounges, the cushioning should feel comfortable and luxurious. Good builders use 4" of cushioning, and high-end manufacturers go the extra step with 5" to 7". You'll appreciate the extra depth during a long cruise.
Many V-berths claim to be a queen when they're closer to a full. Find a friend and lie down on the berths side by side. The best builders use innerspring mattresses.
Most boats have side ports in the cabin, but manufacturers that go the extra mile fit each port and deck hatch with screens for bug-free breezes.
Sit on the head and open a copy of your favorite tabloid. You should have at least 2' of space around you, which you can measure by spreading out both pages of your newspaper.
Place a glass on its side on the galley countertop and roll it toward the edge. It shouldn't roll off. There should be fiddles-raised edges at least 1" high-to keep things on the counter.
Although fiberglass cabin "pans" have replaced wood, "stick-built" interiors, remember that service access is superior with the "inferior" wood.
Where you can, reach behind the cabinet structures in the salon and galley. You're hoping to find that they're bonded in place with adhesives or fiberglass as well as being screwed into position.
Reach into a locker with your hand and feel along the back corners. Spikes of fiberglass can catch your skin or tear stowed gear. Too many builders forget to clean this up. Locker openings should be trimmed in plastic, vinyl, rubber, or aluminum. Ski lockers should be lined with molded plastic or a soft nonporous foam.