Setting environment variables on OS X

Question

What is the proper way to modify environment variables like PATH in OS X?

I\'ve looked on Google a little bit and found three different files to edit:

Answer 1

The $PATH variable is also subject to path_helper, which in turn makes use of the /etc/paths file and files in /etc/paths.d.

A more thorough description can be found in PATH and other environment issues in Leopard (2008-11)