To find it definitively:
1. Consult a repair manual: A Haynes or Chilton manual specific to your year and model will have a diagram showing the exact location. This is the most reliable method.
2. Look near the oil filter: This is the most common area. The oil pressure switch is usually a small, cylindrical sensor with one or two wires connected to it.
3. Trace the oil pressure gauge wire: The wire from your oil pressure gauge will lead directly to the switch. Follow the wire back to its source.
Caution: The engine will be hot if it's recently been running. Allow it to cool completely before attempting to locate the switch.