PATH=$PATH:/new/pathto the end of /etc/profile.
This is because this is the "answer" that many people provide when you do a Google search on how to do it.
However, in Ubuntu the default path is not set in this file so I have always had the feeling that this is not the "right" way to do this. There must be somewhere else that holds this info?
Well I just discovered it.
The system path is set in /etc/environment.
Here is the default path;
brettg@jupiter:~$ cat /etc/environment
To add a path simply stick a colon at the end followed by your new path;
Easy peasy! (When you know how)
This does not apply to debian (squeeze), the system path is set in /etc/profile same as other systems.