run rats nest to ensure all is connected
run DRC
ensure non-plated through hole (e.g. mounting hole) have copper clearance (else it will be manufactured as plated hole)
ensure outline is present and uses 0.1 mm lines
ensure the text next to the LEDs, header pins, and test points are the right ones
remove floating trace stubs (disable pad/subcircuit visibility, and show planes as wireframe)
place project/board name and version
place ordering number text under a component, or on panel rails
place reference designators for assembly
check solder mask (e.g. tented holes) and solder paste (e.g. through hole pins)
check outline copper pullback
check output gerbers
print gerber and place components to check footprints (particularly if new) and spacing