I use dxf -> accutrans -> modo, although modo has DXF import I prefer to use accutrans as it has more options.
For those that don't have AutoCAD for DWG to DXF one can use use software such as the A9 convertor:
http://www.a9tech.com/products/a9converter/
Also, DWG TrueView (free from AutoDesk) is useful for converting DWG from the latest versions of AutoCAD to earlier incarnations. This can help if you're having compatibility issues when using DWG to DXF convertors.