WARNING: IFC import and export is under continuous development. This page may not contain the most recent information.
REVIT ADD-INS
There are Revit Add-ins for better IFC export.
Problems and solutions are usually software specific. If you know what software is going to use your IFC export look for add-ins from that software manufacturer.
There is an open source one at:
http://sourceforge.net/projects/ifcexporter/
RESOURCES
IFC Exporters and Importers and Tips
http://whatrevitwants.blogspot.com.au/2012/04/ifc-exporters-and-importers-and-tips.html