Preparation of VLTI observations

This paper provides a step-by-step overview of the most important issues that should be addressed by astronomers planning a VLTI proposal or observing run. Each problem is first presented in general terms, along with guidelines on how to address them. In addition, the entire procedure is illustrated for the case of a realistic observing scenario. Illustrations for this tutorial are largely based on the JMMC-distributed ASPRO-VLTI software, which provides the user with quantitative and graphical information that can be helpful in preparing VLTI proposals and/or observations.