This paper aims to complement the OECD Recommendation of the Council on Consumer Protection in E-Commerce by elaborating on its key principles in the context of online advertising and offering practical guidance on how to apply these principles. For these purposes, the guide provides a number of good practice examples from policy makers, consumer enforcement agencies, and stakeholders that are relevant to the key principles. Building on those examples, the guide also offers tips for businesses in four areas of online advertising: (i) misleading marketing practices; (ii) ad identification; (iii) endorsements; and (iv) protection of children or vulnerable consumers.