This briefing paper aims to support decision makers at research organisations and research funders to develop new monitoring exercises or assess and improve existing processes to measure the Open Access status of publications. The availability of data and information on the current state of scholarly publishing is invaluable to help advance Open Access. Given the complexity of the scholarly publishing system, this involves a multitude of decisions. This briefing paper provides recommendations on the three main questions an organisation should answer to develop a monitoring exercise: Why, What, and How? Examples of different monitoring exercises have been selected to represent different use cases, organisational setups, data sources, and strategies of interpretation.