New houses and established gardens need different details
On a building site, identify the entrance, the person responsible for access and any equipment operating near the sighting. Leave pipes, sheeting and materials where they are until the area has been assessed. A snake that was visible beneath one item can become much harder to locate after a hurried search.
At home, report whether it is beside the shed, under a deck or inside the building. Keep children and pets away from that route. Do not ask a neighbour to catch it or use a hose to push it out. A calm call with accurate information is the better first step.