Stupid question deserves....
Park it on the ground - never leave it in the air!
Last week I flew a substantial portion of the Australian East coast for fun and only parked at an airport 1 night in 10. Why would anyone need advice on where to hangar a helicopter unless they had a helicopter type that cant stand the dark or disolves in water. Sounds like a 'must have an airfield' fixed-wing pilot mentality.
OOW
Places I parked on my trip last week were:
Beach
Boat ramp car park
Campsites
Private garden
Cricket pitch
Petrol station x 2
Hotel lawn