The American Petroleum Institute (API) Manual of Petroleum Measurement Standards (MPMS) Chapter 14.1, Collecting and Handling of Natural Gas Samples for Custody Transfer, provides practical guidance for gas sampling in custody transfer applications. Though gas sampling should not be performed without fully reading the standard, this paper is designed to provide supplemental information, illustrative examples, and guidelines for how best to use API 14.1. Specific sections of the standard are highlighted and broadened with additional detail. Special emphasis is put on the accurate sampling of an unknown gas stream.