What component is low on oil? The engine, transmission, power steering? That will help to narrow down the possible places to look. If power steering it will be the pump, hoses or rack, if engine or transmission a seal or gasket. Was the oil filter changed recently? If the old gasket stuck to the block it will cause a big leak.
If it is a really bad leak look for the cleanest area around the point of dripping, dirt will not accumulate where the oil is flowing. Just follow the trail back to the source of the leak.