I\'m following a tutorial called Starting a Django 1.4 Project the Right Way, which gives directions on how to use virtualenv and virtualenvwrapper, among other things.
I use an approach that I think is easy to maintain. It also works well if you sometimes use Ubuntu systems, however I will be sure to address the OP's OSX requirement in my answer.
Create a .aliases file with your alias(es) in your home directory, e.g. ~/.aliases
Execute this file from your .bashrc file (this is executed each time for a new shell process) with source ~/.aliases. This is all you would actually need to do for Ubuntu btw.
On OSX call .bashrc from your ~/.profile file, i.e. have ~/.bash_profile contain: source ~/.bashrc