When we rewired our house we put in two panels side by side in the
basement - the main one fed from the meter and a second (smaller) panel that
carries just the 'emergency' circuits.

We put a two pole breaker in the main panel and fed it to a dryer outlet
adjacent to the main panel and just under the emergency panel.

We connected a dryer pigtail to the feeder lugs in the emergency panel and
plugged it into the dryer outlet from the main panel.

The generator feed comes from the external generator location to another
dryer receptacle near the first one. We also connected a single ceiling
light fixture directly to this feeder.

When the power fails, we crank up the generator, unplug the dryer pigtail
from the main panel and plug it into the generator receptacle. Seems like
this always happens in the dead of night, so putting the light fixture on
the generator feeder allows easier access to the arrangement... The voice of
experience..

Cost about 20 bucks for the pigtail and two receptacles. Idiot proof. (I
think)

Carla