Its always a good idea to use Virtualenv. Here you can find the most important commands:

Create virtual environment:

MacBookAir:~ florianzyprian$ virtualenv my_enviroment

Activate virtual environment:

MacBookAir:~ florianzyprian$ source my_enviroment/bin/activate

Deactivate virtual environment:

MacBookAir:~ florianzyprian$ deactivate

Store installed packages in requirements.txt

MacBookAir:~ florianzyprian$ pip freeze > requirements.txt

Install packages from requirements.txt

MacBookAir:~ florianzyprian$ pip install -r requirements.txt

For more details check additional tutorials, e.g:
http://www.simononsoftware.com/virtualenv-tutorial/