I use two ways to manage paths in Mac OS X:

• ~/.profile
• /etc/paths.d

I use the first option when trying things out, and the second for managing the path more permanently.

Example

And example of the using /etc/paths.d to include the git executable in PATH:

• edit /etc/paths.d/git
• Add line: /usr/local/git/bin

When you start a new Terminal session, the files under /etc/paths.d are read, and all paths found are appended to the PATH variable.