Look and listen for activity. Carpenter ants sound like crinkling cellophane. Check frass piles for materials such as wood, insulating, plastic, etc. Frass material will help indicate specific nest locations. Look for plastic vapor barriers under mulch beds.
Ants trail or nest under the plastic film.
Follow foraging ants carrying the food particles. They're heading back to the nest. Place food in the ants' path, then follow them back to their nests. Be mindful of weather conditions during the inspections. They rarely forage if temperatures are below 55 degrees F. 13.