Here is the answer of the steps Experience Manager goes through so that you get a better idea of which modules to troubleshoot: http://stackoverflow.com/a/10802033/1284894.

The issue is usually due to a bad configuration of the Ambient Data Framework including the Request Filter and cd_ambient_conf.xml, or the cd_storage_conf.xml files on either the application or the web service.

Also, Albert has written a blog about configuring XPM and discusses how to resolved some difficulties when setting it up: http://albertromkes.com/2013/01/24/troubleshooting-the-sdl-tridion-experience-manager-with-session-preview/

Here is the answer of the steps Experience Manager goes through so that you get a better idea of which modules to troubleshoot: https://stackoverflow.com/a/10802033/1284894.

The issue is usually due to a bad configuration of the Ambient Data Framework including the Request Filter and cd_ambient_conf.xml, or the cd_storage_conf.xml files on either the application or the web service.

Also, Albert has written a blog about configuring XPM and discusses how to resolved some difficulties when setting it up: http://albertromkes.com/2013/01/24/troubleshooting-the-sdl-tridion-experience-manager-with-session-preview/