Phase noise is one of the fundamental metrics for oscillators. An experienced engineer can tell a lot about the quality of an oscillator and whether it fits the application by looking at the phase noise plot. RF engineers focus on the phase noise levels at certain carrier offset frequencies to make sure that the required modulation scheme can be supported. Professionals designing high speed serial links like 40GbE will apply a band pass filter to phase noise of a reference clock, integrate it, and convert it to phase jitter to predict the bit error rate of a system. This application note starts with a brief theoretical overview of phase noise and methods of phase noise measurement, and then focuses on practical phase noise measurement recommendations such as properly connecting a signal under test to the instrument, setting up the phase noise analyzer, and choosing appropriate settings. All measurements in this document are taken with a Keysight E5052B phase noise analyzer which is one of the most common instruments in North America for measuring phase noise.