The most reliable way is using the source software. You can use tools like the Spatial Manager for AutoCAD to export data directly to KML/KMZ. You will need to select a coordinate reference system so the drawing lands in the correct location on the globe.
If you have the source DWG, use specialized plugins or built-in tools: dwf to kmz
A highly compressed vector/3D format used for sharing CAD designs. The most reliable way is using the source software