The FAIR principles refer frequently to metadata as a key enabler in discoverability, but also having a major role in accessibility and reusability. Publishing structured metadata on the web can provide a simple and efficient means to increase the FAIRness of research resources: it exposes metadata contained in web pages through a formal mechanism, allowing systematic collection and processing by web-based crawlers. Efforts to adopt structured metadata within and across domains would benefit greatly from a set of recommendations that would help ensure consistent implementation leading to enhanced discoverability and accessibility of data. Based on community consultation and subsequent work, this guidelines provides nine recommendations to support the process of publishing structured metadata on the web, namely: Recommendation 1: Clarify the purpose(s) of your markup Recommendation 2: Identify what resource are to be marked up with structured data Recommendation 3: Adopt or develop a crosswalk from a repository schema to markup vocabulary Recommendation 4: Incorporate external vocabulary if it helps to improve data discoverability and interoperability Recommendation 5: Implement markup syntax consistently by following community practices Recommendation 6: Be friendly to web crawlers Recommendation 7: Make the best use of available tools for mapping, generating and validating structured data Recommendation 8: Document and share every step Recommendation 9: Find and join a community, and follow their established practices