You can share your screen (join.me is a good solution) but the real way of doing it is to share you terminal / console.
The best way of doing this is using screen multiuser option.
The procedure es staightforward:
1. open a screen session (-S give a session name):
screen -S screen-multi2. activate multiuser mode
:multiuser on3. the other user (connected to the same server) has to:
screen -x screen-multiAnd thats it, both will see the same session and can write at the same time on it.
More detail about this procedure: http://ubuntuforums.org/showthread.php?t=299286