Copiapo is a city in Chile in Region III de Atacama.
North & West Caldera, Antofagasta
Walk in direction north west from the center onto the Ruta 5 parallel to a train line. There's a roundabout you can use to get onto the road or walk a little further to get to the COPEC gas station, where you can calmly ask people for rides going to Caldera, Bahia Inglesa, Chañaral, Taltal and Antofagasta. On the weekend many people just go to the beach so they are usually not going very far. Try asking for the "peaje" (toll) instead, which is 30 km from Copiapó on the highway. Long distance trucks will pass by there.
Other useful info
Copiapó was the setting of a huge mining accident in 2010, during which 33 miners got trapped underground for 69 days. It's a likely topic to come up in the car when hitching around this area.