Since you are in Xfce4, that is easy to configure, just login as normal user (not root) then:
Click Menu -> Settings -> Removable Drives and Media -> then tick whatever choices you want...
You have choices like 'mount removable media when hotplug', run programs, etc. Also configure Menu -> Settings -> Session and Startup -> under General tab tick 'Automatically Save Sessions at logout' to save your configuration for future logins. Then logout from X and login again as the same user. Check if it works; if not, come back for further help.
Hope that helps.