I am struggling to get XPM preview to work in Tridion 2013, and I am not sure which steps to take exactly to solve this issue.
I can open the Staging website pages in the CMS context (frame). I can edit pages using XPM functionality. I can see items being created in the Preview Session DB. But when I select the "Update Preview" button, it says "Loading..." and afterwards I see the exact same page as before, without my changes. I have the web.xml, cd_storage_conf.xml and cd_ambient_conf.xml as per the 2013 documentation.
What steps do I need to take to get to the root cause of this?