I've done this multiple times. Although it is with a Windows host and Linux guest, the steps are the same.
To access a host share:
1. Ensure guest additions are installed on the guest.
2. Create a folder in host to share (do not need to share on network)
3. In Vbox GUI -> Shared folders, create share for guest (this will be the folder in the previous step (Click automount and remember the name for later))
4. In guest's home folder, create mount point i.e. /home/user/UniqueName (You can do this in Dolphin, Konqueror, whatever)
5. As root, put this line in guest's /etc/rc.local (This will make the mount permanent)
mount -t vboxsf -o rw,uid=500,gid=500 hostfolder /home/user/UniqueName
NOTE: hostfolder is only the name you gave the folder in step 3 not the path; Vbox takes care of the path
6. Reboot guest
Hope this helps