The recommended way to install all the necessary packages is by using Macports.
Be aware that it can take around an hour to install everything using Macports, as all the packages are compiled from source.
An alternative is to use the Free Enthought Python Distribution (EPDFree). Enthought sponsors much of the development for NumPy and SciPy. EPDFree is a bundled binary distribution of Python including a set of useful packages that is quick to install. However, there is no version for 64-bit machines, which means you’ll be missing out on some performance improvements if you have a 64-bit machine.