I'd say echo $PATH
To add a directory to the path, say the bin directory in your home folder, simply type as follows:
The PATH environment variable is a colon-separated list of directories and in the line above we set the $PATH to what it was before, plus the ~/bin directory.
If you want to add a directory for to the path for all users you could put something like this in your /etc/profile:
If you want to just do add it for yourself, add the above line to your ~/.bashrc and make sure ~/.bashrc is sourced (executed) from your ~/.bash_profile.