Adding directories to the Mac OS X PATH variable

See what's in the PATH variable
  Open Terminal -> Type echo $PATH

This will display whatever is set in the path variable. 

Add more directories to the PATH variable
    Open Terminal -> Type export PATH=new_directory:$PATH

This will add the new_directory to the PATH variable. If you want to make this change permanent simply redirect the above to your .profile file (You can find it in your home directory.. If not, you can simply create one). See below for an example of redirection... 

Open Terminal -> Type export PATH=new_directory:$PATH >> ~/.profile