  This document describes analytical and numerical techniques for the
generation of Gaussian density fields, which represent cosmological density
perturbations. The mathematical techniques involved in the generation of
density harmonics in k-space, the filtering of the density fields, and the
normalization of the power spectrum to the measured temperature fluctuations of
the Cosmic Microwave Background, are presented in details. These techniques are
well-known amongst experts, but the current literature lacks a formal
description. I hope that this technical report will prove useful to new
researchers moving into this field, sparing them the task of reinventing the
wheel.
