Here are some of the best posts I've found detailing the process of setting up Python with pip, virtualenv and virtualenvwrapper. I recommend that you read through these first.
- https://coderwall.com/p/a5mz9a
- http://jontourage.com/2011/02/09/virtualenv-pip-basics/
- http://sergeykarayev.com/work/2012-08-08/setting-up-mountain-lion/ — including SciPy install details.
- http://simononsoftware.com/virtualenv-tutorial/ — some decent info for new users.
My install process is detailed in the following gist