I need to autostart skype.
/etc/xdg/autostart/skype.desktop - not working
/etc/xdg/lxsession/Mint-LXDE/autostart + line @skype - start skype twice
/etc/rc.local + line skype - not working
Try putting the skype.desktop file into the ~/.config/autostart/ directory.
Just to make sure: does your skype.desktop file contain the necessary parameters, and does it point to the correct location of the skype executable (in case you didn't get it off the repository)?