There are several things which one can change after installing ubuntu and using SSH. Here are some of the things which I would do, along with their descriptions (in red):
Sample changes in ssh_config file (found at /etc/ssh):
ForwardX11 yes Forward X11 display
ForwardX11Trusted yes Forward X11 display only from trusted sources
ServerAliveInterval 5 Send small packets of data every 5 seconds so that SSH connection does not time out
